Should the more snowbally champs even exist?

I mean so much of this game is about teamwork and positioning. The only time you see characters like Yi or Kat ruin a game its because matchmaking gave them one or more opponents who had no idea what they were stepping into. This makes the lowest skilled players on any team much more of a liability and probably increases toxicity since when the 8/0 LB comes and erases your bot lane people are generally gonna start cussing at the mid.

Allowing champions to snowball as hard as someone like Vayne or Ekko just removes the team aspect of the game and makes it more of a one man show. After long enough the entire game becomes about that one champ, where if you can just remove them from the equation, you win the fight. To me this is the exact opposite of what you should want out of a team based activity. It's neat to have a star player and all, but when someone can get so fed that they can easily 1v3 the enemy team, something just isn't working out right.

Why not reign them in some? If the idea of a supreme snowballer has to stay, then why not give them significantly horrible early and mid games? I mean all Kat or Vayne really need is like a 2 kill lead and nobody can compete with them unless you do something really drastic, and even then you're risking getting them even more fed. I don't see how that level of snowball is good for anything except making teams fight amongst themselves even more.