I mean, that's all they really do these days too. I've been playing since season 2 and there are definitely ups and downs across the history of the game. These days they've slowed down on new champs, like 2 a year or so. They've maybe gone a little trigger happy with item changes, but it doesn't bother me or my friend group too much. Like I said, gives us more opportunity to theory craft and less time for boring stale metas to set in. Game modes got boring for a while, but they're doing better these past couple years (Arena 2v2s is one of the best modes they've ever released)

As far as ruining it for people who like it how it is, I don't know anyone who fits that, but it's definitely possible people are getting alienated by changes. But I think it's okay alienating that small minority to keep the game alive and fresh for the vast majority