Regarding your point on not being able to be matched up against blocked players:
This is not healthy for a game with matchmaking to allow players direct control over its matching system like this. In a PvP game this would especially be a problem, but it has problems in PvE games as well. In this situation, meta players would just block other non-meta players, effectively lowering the matching pool to two different queues in a single large pool. In this scenario, it would be more efficient for the matchmaking system to just have two separated queues, which brings me to the next point.
I would argue the opposite. Vermintide 2 employs this exact thing and it’s been working pretty well - it actually does punish people who get blocked a lot by other people, and if you’re being blocked by a ton of people, there’s probably more than just “skill issue” and “you’re not running meta” going on. You do get sweaty people who block non-sweaty people, yeah, but it’s not hampering the community of the game in the slightest - and that game is waaaaaay smaller in size than something like Helldivers where you can get blocked by a ton of people and still play with other people due to the sheer size of the playerbase.
“Now, there’s this one thing that keeps puzzlin’ me, Mr. Godzilla… if your shoe size was 500 like you said it was, and you said you weren’t stompin’ over in New York City in 1998… then who else could have a shoe size of 500 stompin’ all over New York City? Couldn’t have been Mecha-Godzilla, nobody’s seen since him since ‘93.”