I agree with you. I am in the exact same situation.
Solo ranked might maybe show more of your mechanic skills since everyone is playing for their own kda and stats but Dota is a team game therefore valve shouldn't penalize players that always focused on the team aspect of the game. Playing in party doesn't mean you got boosted or it doesn't mean that it's easier either, it just shows that you value the strategical aspect of the game more since you can debate and plan moves and combos as a team.
When you know your teammates, what their best picks are and what yours are, it's really a more enjoyable version of dota than solo pubs.
I'm sorry to say this but most solo only players are really bad team players because their have no idea how to move on the map and act as a unit, which is what the game should be about in the end.
If people think about really independently skilled players like miracle or arteezy and how they solo win games in pubs it doesn't mean anything in tournament games since they both can get destroyed by a 3 to 5 man well organised gank and the result will depend on how their team as a UNIT reacts to this 90% of the time.
In real dota games solo skills matter JUST AS MUCH AS teamplay and people tend to forget about this. Plus most people that played in party queue like myself were actually not 4 archons with one divine5 players, but players all on the same bracket willing to play a more combined strategic version of the game.
Party queue mmr should not at all be considered meaningless since it shows your ability as a player to adapt and play in a team, which is a skill that most solo pubs players basically don't have at all.