#StarCraft (1998) had a unit selection limit of 12 at a time, and partly due to that, even pro matches were wild and all over the map.
In #StarCraft2 the limit was lifted, resulting in matches revolving more around "death balls" of entire armies, and it lost a lot of the chaotic micromanagement that many people found so fun.
It's a good example of how QoL isn't always for the better, or how arbitrary restrictions that might seem questionable (i.e. why 12?) can enhance a game.
Another example might be the (gold) auction house from Diablo3, which though it technically only streamlined trading, completely undermined the entire loot system.