think about it from this perspective:

if you did not lose anything because of a leaver then why would anybody ever stay for a game?

every single game would have a leaver and it will almost always be coming from the team that is about to lose.

people will have throw-away accounts dedicated to making sure their team didn't lose any SR or players would just constantly bully other players into leaving so the other 5 players did not lose anything.

this will 100% be exploited/abused. i can confidently tell you that if i did not lose SR because of a leaver. i would NEVER lose SR every again.

Is there no other solution than saying "suck it up"?

well why do you only complain when you lose SR? why don't i ever see threads where people complain about gaining SR unfairly because the enemy team had a leaver?

assuming you are not leaver. the enemy team has 6 chances for a person to leave. you only have 5. you technically have a better chance than the enemy team. it evens out. you lose games because of leavers and you sure as hell win games when the leavers are on the enemy team. it should be somewhat equal.