Wasn't it better when only .com mattered? There are thousands of TLDs now and that forces companies to buy multiple, these domain names are not even memorable anymore specifically because of the TLD part.

Well, it depends. If all you were interested in was getting a "good" (e.g., short) name in .COM, no.

In the late 90s, when NSF allowed Network Solutions to charge for domain names, people complained that they (now Verisign) had a monopoly, so after a number of fine lunches and dinners in far off exotic places (see https://en.wikipedia.org/wiki/IAHC), there was a proposal to create more top-level domains, created the registry/registrar split, proposed the Uniform Dispute Resolution Policy (primarily for Intellectual Property owners), etc. Then, the US government stepped in and started a process that led to the creation of ICANN.

The whole point of this exercise was to introduce competition into the domain name system. It did with the registry/registrar split and tried with the registries by having multiple rounds of a limited number of new top-level domains. However, the latter was kind of stupid (IMHO): the switching costs for changing TLDs is way too high for the existence of new TLDs to significantly impact Verisign's monopoly -- instead, it created a bunch of monopolies.

However, people weren't happy with the "limited number" part of ICANN's efforts to introduce competition in the TLD space, so in 2012, the ICANN community (which anyone can be a part of) opened the flood gates, removed the arbitrary restrictions on how new top-level domains could be created, and we now have over 1500 TLDs.

It's still basically only .com that matters. There are those few others that matter commercially (setting aside the org for nonprofits and edu and gov), such as .io, but for every 'clever domain' startup, I see 6 more who, unable to get say, frog dot com, go with something like "usefrog dot com" or "tryfrog dot com" in their early days and come back and snap up frog dot com after they get their Series C. They could have gotten say, frog dot legal or frog dot engineering but nobody wants those.