Games like Among Us, RV There Yet, Peak, Lethal Company, etc. I don't mind them so long as there's no woke elements to them, though I've never actually played any of them myself. I have two groups of streamers that I like (Fooster/Fisk/Olafpawbelt and Splitsie/Capac/TFE/Shack) that play them from time to time and it's pretty enjoyable watching them. These sorts of games strike me as games that are more meant to be watched than played yourself. I doubt many of them sell that many units, and they typically are only popular for a couple of weeks before being replaced by the next one.
I bet a lot of copies sold are people who think 'oh man, this looked like fun when I saw $streamer play it, I can't wait to play it with my friends' and then they never do. They seem to be pretty cheap, so if an indie dev can provide a few weeks of enjoyment for $9.99, honestly there are worse ripoffs in the gaming world.
I've also done Seamless Coop for Elden Ring and Dark Souls 1. No problem setting them up or getting them running. They're not (usually) unstable. No real lag (though we're all within a couple miles). Just a few weird hitches involving NPC dialogue, and the balance is questionable no matter what settings you use.
Desyncs are a real fucking bitch, however. In Elden Ring, desyncs will just cause you to crash pretty much any time the world updates. We got a desync because I unlocked a grace when one of the players wasn't connected, and she apparently didn't get the update when she rejoined, so we had to have her go through everything we had done step by step while she wasn't connected. However, this is probably preferable, because at least you know what went wrong.
In Dark Souls 1, the desyncs kneecapped the game, and I could not tell you why it happened. Even though we were able to get through the game, most NPCs post-Gargoyles either disappeared, looped their death animation, or didn't respect quest flags. We lost all access to pyromancy as a result. More importantly, Ingward despawned without dropping the Key to the Seal, so I had to use Cheat Engine to move myself past the door, and Dusk was completely broken, so again, I had to use Cheat Engine just to access the DLC.