Teamfight Tactics isn't a rotating game mode, stop whining about Nexus Blitz
This is literally a different game. This isn't playing a game of LoL but with some different rules, you don't have 4 abilities with cooldowns and a passive. You don't move your one character but right clicking on the map. You don't navigate the map freely. You are not playing on a team.
Complain about it being a rip off. Complain about it being boring. Complain about it being a cash crab or whatever other shit you want to gripe about. But this isn't taking away your Nexus Blitz. This is not a new game mode that is occupying the same space as the main game, this is a separate game with different gameplay mechanics that will appeal to different people. Stop being a bunch of petulant children!