I understand that everyone is tired of requests like "Advise CMS", but let's be supportive of the greens.
I need to choose a CMS for the site. Requirements are:

    dоcument Tree
    Ability to attach fields to them (groups of fields, files, etc.)
    User-friendly design template creation scheme
    Adequate modules for a simple catalog of goods, an online store with plushies (including delivery and payment by cards), with a maximum of 5000 products (books, compacts, and other educational materials), as well as a simple forum.
    Should work easily on lamp/famp-shared hosting, with up to 2000 visitors.
    Free of charge is preferred.

In general, I have been struggling with MODx Evo for quite a while, and I like it because it's easy to work with templates, has a dоcument tree, and allows for televisions (TV). However, I couldn't get along with Shopkeeper. Moreover, MODx Evo seems to be outdated, and Revo, as others say, is too heavy. But I haven't experienced it myself yet, so maybe everyone is mistaken?

And it all started when this website (without a catalog though) was built on Joomla (back when I was young and foolish), and now I don't see a reason to upgrade to the next version (especially since there is no straightforward method for migration), but I have a strong desire to change everything completely.

MODx Revo combined with minishop is a great choice for building an online store. Alternatively, Drupal paired with Ubercart also offers pre-built assemblies for creating an e-commerce platform.

The combination of MODx Revo and minishop provides a robust solution for setting up an online store. The flexibility of MODx Revo allows for easy customization and the ability to handle complex website structures. With the addition of minishop, managing products and transactions becomes straightforward and efficient.

On the other hand, Drupal, a powerful content management system, can be integrated with Ubercart to create a feature-rich online store. Ubercart offers a range of built-in functionalities for product management, payment processing, and order fulfillment.

Both options have their merits, and the final decision depends on specific requirements and preferences. It's important to consider factors such as ease of use, scalability, and available resources when selecting the ideal CMS and e-commerce platform for your online store.

Take a look at HostCMS.
The implementation of an online store, complete with features such as a shopping cart and delivery options, is already available.

The free version of HostCMS offers all the necessary functionality, with the exception of a forum, which requires upgrading to the commercial version.

HostCMS provides a comprehensive solution for building and managing an online store. Its free version includes all the essential features needed to run an e-commerce platform effectively. However, if a forum is a crucial requirement, opting for the commercial version would be necessary.

With HostCMS, you can create a seamless online shopping experience for your customers while enjoying the benefits of a user-friendly content management system. Explore the capabilities of HostCMS and consider upgrading to the commercial version if the additional forum functionality is essential to your website.

Give ezCatalogCMS a try. It provides a product category tree and allows you to add custom attributes to your products. It offers both a product catalog mode and an online store mode. However, it does not have a built-in "Forum" module. Nonetheless, you can easily integrate any third-party forum software, such as phpBB3.

Three years ago, I had experience working with MODx Evo, which was quite an unconventional engine. At one point, I decided to migrate to Revo. However, during the transition, I encountered significant performance issues and ultimately reverted back to Evo.

The process of migrating between content management systems can be challenging, and the suitability of a new platform may not always align with expectations. It is important to thoroughly evaluate the requirements and potential drawbacks before proceeding with a migration.

Choosing the right CMS for your website can be a crucial decision. Based on your requirements, here are a few CMS options you may consider:

1. WordPress: It has a dоcument tree-like structure with categories and tags. You can attach custom fields using plugins like Advanced Custom Fields. It offers a wide variety of user-friendly design templates through themes. There are several e-commerce plugins available for creating an online store, such as WooCommerce. WordPress is known for its extensive plugin ecosystem and should work well on shared hosting with the specified number of visitors. Additionally, it has a large community and plenty of resources available.

2. Drupal: It provides a hierarchical content structure similar to a dоcument tree. You can attach fields to content types using the built-in Field API. Drupal has a flexible theming system that allows for the creation of customized design templates. It offers modules like Drupal Commerce for creating an online store and Simple Forum for a forum. While Drupal can be resource-intensive, it can still work on shared hosting if properly optimized.

3. Joomla: Since you have previously used Joomla, you might be familiar with its interface and structure. It offers a dоcument tree-like structure and the ability to create custom fields with extensions like Fabrik or ChronoForms. Joomla has a template system for design customization. However, the availability of quality modules for an online store and forum may be limited compared to alternatives like WordPress and Drupal.

4. Grav: If you prefer a flat-file CMS, Grav is worth considering. It offers a hierarchical structure, supports custom fields, and has a flexible templating system. There are plugins like Shopping Cart for creating an online store and Grav Forum for a simple forum. Since it is flat-file, it does not require a database and is known for its speed. However, it may require more technical know-how to set up and customize.

5. Magento: If you are looking for a CMS specifically designed for e-commerce, Magento is a popular choice. It offers advanced catalog management features and supports a large number of products. Magento provides a user-friendly interface for managing an online store, including inventory, payment options, and shipping. However, keep in mind that Magento can be resource-intensive and may require more technical expertise to set up and customize compared to other CMS options.

6. Shopify: Another CMS focused on e-commerce, Shopify offers an easy-to-use platform for building and managing an online store. It provides a wide range of customizable templates and intuitive design tools. With built-in features for product management, inventory tracking, payment processing, and shipping, Shopify simplifies the process of creating an online store. It is a hosted solution, so you don't have to worry about hosting or server maintenance. However, note that some advanced features may require additional paid plugins.

7. OpenCart: OpenCart is an open-source CMS specifically designed for building online stores. It is lightweight and offers a user-friendly interface for managing products, categories, and orders. OpenCart provides a range of free and paid extensions to enhance the functionality of your online store. It should work well with the specified number of products and visitors on shared hosting. However, keep in mind that OpenCart may require more technical knowledge for customization compared to user-friendly CMS like WordPress.

8. PrestaShop: PrestaShop is a popular open-source CMS focused on e-commerce. It offers a wide range of features for managing products, inventory, orders, and payments. It has a user-friendly interface and provides customizable templates for designing your online store. PrestaShop also has a large community and marketplace for extensions and themes that can enhance the functionality of your website.

9. Craft CMS: Craft CMS is a flexible and user-friendly CMS that allows you to create customized content structures and attach fields to them. It has a clean and intuitive interface for managing content and a robust templating system for design customization. While Craft CMS is not specifically focused on e-commerce, you can integrate it with popular e-commerce platforms like Shopify or WooCommerce to add online store functionality.

10. Contao: Contao (formerly known as TYPOlight) is a versatile CMS that offers features like a dоcument tree structure, customizable templates, and the ability to attach custom fields. While it may not have as many third-party modules and extensions as some other CMS options, it provides a solid foundation for building websites with various requirements, including an online store and a forum.

11. Ghost: Ghost is a lightweight and modern CMS primarily focused on blogging and content publishing. It offers a simple and user-friendly interface for creating and managing content. While it may not have out-of-the-box e-commerce or forum functionality, you can integrate external services or plugins to add those features if needed. Ghost is known for its speed and performance, making it a good choice for smaller websites with a focus on content.

You're stuck in the past if you're still considering MODx Evo. It's an outdated relic that's been surpassed by more robust and scalable CMS platforms. Joomla? Please, it's a bloated mess that's only good for legacy projects. And  Revo, which is a resource-hungry beast that's only suitable for large-scale enterprise projects.

If you want a CMS that's easy to use and scalable, you need to look beyond the tired old options. WordPress is a good starting point, but even that has its limitations. I'd recommend exploring newer, more innovative CMS platforms like Gridsome or Next.js, which offer a more modern and flexible approach to building websites.