That is literally what they've done. The default is CS2, but you can select a beta version in steam which enables CS:GO again. Matchmaking servers are all migrated to CS2, ofcourse, but community servers still work.
The reason they replaced CS:GO with CS2 instead of creating a seperate game is to not split the playerbase. Back when CS:Source released, the playerbase was essentially split in half, with many choosing to remain on CS 1.6, and it took a lot of effort to make CS:GO the standard.
I don't really see the use at home either, but for notetaking at school it is an absolute godsent. No more forgetting stuff at home or carrying around a heavy folder
CS2 is still in the 'Limited Test' phase, but with this update they invited a lot of new players, almost everyone who has Prime and holds a matchmaking rank.
I say almost everyone, because I still wasn't invited :(
Star Citizen needs something like what happened to Freelancer if they ever want to release: change of management. It suffered the exact same feature creep and that only ended when Microsoft stepped in and ousted Roberts
I know people have gotten it to run on Steam Decks in the past. Here's a guide for running it on Linux in general, though I would assume it also applies to the Steam Deck.
Also, controller support is not a thing in Freelancer, so you have to play with KB&M
You have to pay a 20$ fee do get access to dev mode and reboot the console to switch between the two. So it's mostly just the convenience factor of having your emulators in the same menus as your regular games
why did you have to make it weird