About featured game modes

So, I've been thinking for a while about the fact that featured game modes are temporary. I totally understand the multitude of reasons for Riot not wanting to have modes that are intentionally unbalanced (or have strange limitations such as a Teemo permaban in all for one), and not wanting to devote time to balancing gamemodes that are really just for fun. However, every time a featured gamemode is removed it just feels like content that was often very fun being removed, leaving the game missing something. The problem as I see it is, gamemodes are removed and replaced with nothing. Enjoyable content is removed from the game, and then... that's it. Wait a couple months for some new content, maybe. I feel like there should be a featured gamemode playable much more often, if not at all times. It reminds me of Left 4 Dead's mutations- weekly gamemodes that would be made unavailable at the end of the week, but no one ever minded because it was being replaced with new content. The way it is now, it feels as if every time there's new content that isn't in the form of a change to SR (new items or whatnot) or a new champion, it just gets removed.