Compared to other companies, Valve let the community use alternative community servers. Even if Valve does not care about the game anymore (sigh, one of may all time favorites), it's possible to maintain community servers. This is something any other game wish to had, without hacking the system; it's just part of the game. And people can even use modded communities and there exist some really cool stuff (admittedly I never tried them, I would play the game if it didn't have the bot problem).
TF2 is almost 20 fucking years old and has been F2P for 13 of those years, why should Valve care to do anything about it? Frankly, the official servers even still being online at all is more than most other games(besides subscription based games like WoW) of that era can say.
Like, what were you guys expecting? For Valve to support the game the rest of your lives?
The last major update was in 2017, bots started plaguing casual mode around 2018/19, and ever since the game has seen anastonishingly tiny amount of updates outside ofhthe usual summer, Halloween and Christmas updates (which just shove community made content from the Workshop into special gamemodes and crates); apart from the recent 64-bit version and the VScript addition a while back, nothing of interest has happened in the last handful of years. F2P lost their ability to call medic and the bot crisis is completely unsolved.
It's sad. But as another user pointed out, at least we have e community servers (and good ones).
TF2 is no longer making a lot money for valve. Veteran players have all theirs special hats/cosmetics and no new player wants to invest time and money in a game so riddled with cheating bots. They could easily handle the situation. Detecting obvious cheating bots isn't hard but valve doesn't even try. Yes, there are community servers, like Uncle Danes, that are good at handling bots, but it's also a big burden for them to constantly ban/remove cheating bots.
Valve is testing server side AI cheat detection in CS2. Let's hope that they will bring that to TF2 valve servers. Maybe don't VAC ban players being detected (AI is buggy), just remove them when detected and maybe disallow them from joining valve servers for a week.