Keep Team Builder!
I don't know about you, but I like TB the way it is. It's the only game style that let's me experiment a new meta. I can't go Alistar jungle in norms, because I would be harassed. And sometimes I just want to break meta and have fun. Instead of being able to pick your champion and role, Riot's "New Champion Select" doesn't even guarantee the position you want, let alone the champ you want. Now, it's back to trolls banning your champ because they have a bug up their ass. I don't care if there's a new game mode. I'll even try it out! But don't remove TB. There's nothing wrong with it.