I'm level 24. I don't want to play against Diamond players.

There should be a level cap for pre-level 30s (level 5-29 only), and no level 30 should be able to queue duo with a level 5 in sub 30. Have level 30 and lower level friend duo in level 30 games only.

hypothetical numbers

level 2 = 200 mmr diamond in normals = 1500 mmr

level 24 ~ level 2 duo queueing with diamond friend

but yeah, I do agree that your normals mmr should be automatically recalibrated to your ranked mmr if it's higher

Seriously. It's annoying when you have a smurf on the enemy team, and it's annoying when you have a smurf on your team.

Then go play DOTA 2, you won't play against any League Diamond players I bet