What are some of your favourite games that have become literally unplayable over time?

Recently, Ubisoft announced that it will close the online services for a number of games. One of my favourite games, Anno 2207, is published by Ubisoft. It's not on that list, but I have a fear that it will not be long before its online services will close too, in part because when Anno 1800 comes out next year, it will neither be the "current" nor the "previous" Anno game (which Anno 2205 will be). So there will be no particular reason for Ubisoft to keep it online: players should just move on to the newer games.

Normally, it shouldn't be a big problem, as online services usually only exist for multiplayer games and features. But in the case of Anno 2207 it's a little bit more complex. One of the core gameplay mechanics is a ship called the Ark, which has permanent upgrades and some item storage, even across games and maps, in single player. So there is kind of a meta game to upgrade it more and more. The publisher or the developer decided to make this Ark function completely online (probably as a kind of DRM measure), so when you're offline you cannot use it at all. No upgrades, no storage. Basically the game is completely gimped by taking a core mechanic out. So when Ubisoft will shut down its online services, the single player mode will be permanently gimped forever (and I have no faith in Ubisoft releasing a patch before they do, and/or putting it DRM-free on Gog like they did with Anno 1404 and previous games).

I was discussing this with a friend, and he mentioned that his favourite game is actually World of Warcraft: The Burning Crusade. While he also liked Wrath of the Lich King very much, after a few expansions he just didn't like the game any more. These days, you can find private servers running The Burning Crusade, but they risk being shut down at any time and in some ways it's just not the same experience (which in part can be credited to nostalgia perhaps).

So another way of a game being unplayable is by it changing so much that the game you once loved basically just doesn't exist any more in that form. With single player games this can be circumvented by trying to download previous versions though (if they are still available online somewhere, legally or otherwise).

Now, it's not just nostalgia, as may be the case with a lot of World of Warcraft players (it's often pointed out that if they would play Vanilla or The Burning Crusade nowadays, they wouldn't enjoy it). Literally every year, I still play games such as Total Annihilation, The Legend of Zelda: A Link to the Past, Half-Life), and the earlier Pokémon) games, and actually genuinely enjoying them. I am just one of those people who sometimes prefers a familiar experience rather than trying something new.

A lot of older games are still playable. In particular DOS games run well using DOSBox and for older consoles emulators are a godsend and do a great job of being able to play those old games on modern systems (not certainly not perfect, and some games do show a lot of issues when being emulated). But there are also a lot games that just won't work, for example 16 bit Windows games and games which were specifically targeted for Windows 95-XP are notorious for having a lot of issues trying to run them on modern (64-bit, Windows 7-10) machines without third party patches.

Unfortunately, there isn't much money for developers or publishers in patching old games. Some embrace older games by fixing them for newer systems (and/or putting them up on Gog), while some release remasters or enhanced editions (eg. Baldur's Gate and Age of Empires 2). But most just leave them alone, to be forgotten by the sands of time. Or, in a lot of cases, being missed by a lot of fans.

What are some of your favourites games that have become unplayable over time, for whatever reason?