My understanding of the system is limited.

However, I have noticed that there are numerous new domain extensions such as .paris, .media, and .today, among others.

I am curious if there have been any instances where a company that owned a domain name ceased operations or stopped paying their annual fees (which, according to my knowledge, can be quite high) resulting in the closure of the domain and causing all the website and domain owners who had invested their time and resources into promoting it to lose everything.

It is true that there have been instances where domains with unpopular extensions have been closed - a process known as "sunset".

This doesn't happen often, but in case such a scenario does occur, the registrar can transfer the domain to another.

Alternatively, the closure may come from the registry itself, as demonstrated in the example of the sunsetting of second-level CentralNIC TLDs as discussed in this blog post: https://iwantmyname.com/blog/sunsetting-of-some-second-level-centralnic-tlds.

Roughly 185/25 regular/annual, quite a lot. But not to the extent of "several hundred thousand".

I have encountered instances where a company owning a domain name ceased operations or stopped paying their annual fees, resulting in the closure of the domain. This situation can have a significant impact on the website and domain owners who had invested their time and resources into building and promoting their online presence.

The sudden closure of a domain can lead to a loss of all the design and development work that went into creating the website. This includes not only the visual aspects of the site but also the underlying code, functionality, and user experience elements. It can also disrupt any ongoing update or maintenance plans for the website, as access to the domain is suddenly cut off.
The concern extends to ensuring that the website remains accessible to its audience. Without a functional domain, the website effectively goes offline, potentially resulting in a loss of traffic, leads, and sales. This can impact not only the website owner but also any stakeholders, partners, or advertisers associated with the site. Moreover, the sudden closure of the domain can cause difficulties in redirecting traffic to a new domain and may require significant effort to rebuild the online presence from scratch.

The non-renewal of a domain can lead to the suspension or termination of the hosting services associated with the domain. This can disrupt email services, databases, and other resources linked to the domain, leading to data loss and communication interruptions for website owners and users.

I understand that the sudden closure of a domain can also affect any custom scripts, applications, or integrations that were developed specifically for the website. Without access to the domain, these functionalities may stop working, leading to a broken user experience and potential data loss.
The impact of a company ceasing operations or failing to maintain their domain goes beyond just the loss of the domain name itself. It can have far-reaching consequences for web designers, webmasters, hosting specialists, and programmers, as they work to mitigate the effects of the domain closure and ensure the continuity of the online presence for their clients or stakeholders.

Noobs jumping on fancy gTLDs without due diligence. These vanity extensions are cash grabs - some registries fold faster than a bad pоker hand. Remember .sucks? Exactly. Stick to .com or .net unless you enjoy playing Russian roulette with your SEO and branding.