Party Ranked is beyond saving
It has finally dawned on me that the issue of rampant smurfing, boosted players, and terrible match quality in ranked party mode will never change. And for one simple reason: there are a LOT of closeted smurfs now. The mentality of smurfing has changed for many people, at least behind closed doors. A lot of them think they are excluded from calling themselves smurfs because "I have to play on this account to play ranked with my crusader friend" or a similar excuse.
Turbo has slowly killed casual unranked for a long time. Groups that may want to play unranked due to having huge gaps in mmr can't find matches because no one is playing it. If they do manage to find a game after a long wait, the match quality will probably be terrible. The higher ranked friend feels "forced" to get a smurf account so they can even get into a match with one another.
There is a vicious cycle here that results in so many boosted players and further ruins the match quality. The cherry on top is lack of a seasonal mmr system.
Change my mind
edit: my mind has been changed on seasonal mmr or at least I realized that I don't understand well enough to advocate for it one way or the other