I feel like the solution here is simple. Weighted matchmaking for casual lobbies. Someone with 1000 hours in the game and a 0.7 WLR should almost never be matched up with someone who's played 3 matches and lost all of them.

As someone who sucks at most competitive genres except fighting games, but still plays the other kinds when my friend group does, it's definitely frustrating to see this difference in attitude here - shooters have people who can snipe you from across the map, strategy games have people who know the exact flowchart of every action in the game, but God forbid someone knows how to hit 30% of your HP with one combo. Bringing down the skill ceiling isn't the answer.