I think you should be able to leave a match for any reason at any time. But if you abuse it, then you ought to have a little time out.
The punishment should be for consistently leaving without rejoining while the match is in progress. That way if it’s an authentic situation, then you face no punishment. And the worst punishment you can face, is a little time off.
Sounds to me the issue is people looking at a team, or a respawn, and thinking they could get a better deal by leaving and re-queuing. I know there are some compelling reasons to do this, but if you do, then you are part of the problem. Add a ~5min timer before you can play again, ya might be less inclined to take the escape pod of spite.
And that’s only for people who leave and don’t rejoin over a threshold of their games. Nice and palatable for the mums & dads 