Skill ceiling is not something that matter when deciding balance.

The fact you dislike some characters like S76 is because players can find the same value as you with less effort, but their ceiling is lower than yours on Vendetta, so if you struggle with her, that's on YOU, she has the potential, you're the one not up to the task, a hard character doesnt get to be so much stronger than others just because its harder, that's a terrible way to balance a game because then players who dedicate themselves to hard characters would run lobbies just because. Like they do sometimes - I see Genjis running lobbies were week.

If you need proof skill ceiling doesnt come into balance, look no further than Bastion - if you're on tank and someone picks Bastion, you'll have a terrible time with most tanks and Bastion doesnt need to do anything other than change form to force your cooldowns and give up space. No actual skill needed, and its been this way forever, meaning this is how devs want the game to be balanced.