Sorry didn't mean to assume I am honestly just having a hard time wrapping my mind around what you are saying.
Instead of me arguing about the thresh/blitz bot combo maybe its not the combo that bothers you but the premade dominance. What I mean is lets say we had the old system and you had two people that really wanted support and they wouldn't budge and one picked thresh and the other picked blitz and you proceeded to wipe the floor with them. If this happened I am guessing you would be laughing at their troll pick and would have never made this post.
This did not happen though because they were a premade and used their increase synergy to destroy everyone. What makes it worse is they did it with 2 champs that are not "meta" which feels like it should have been a "weaker" bot lane than yours. Its like being killed in Call of Duty by some dude with a knife when you have a gun. (Again I am not putting words in your mouth just trying to get to the root of the complaint)
Now I made a post a few days ago that got 0 comments about the matching system. I went from winning most of my games to losing most of my games. I had 4 games strait where I couldn't land a single skill shot, not with blitz, not with morg, and I couldn't even walk up with braum and land a Q. Everyone dodged everything. To make matters worse my team comps have been miserable. I had a team mate in one game arguing we shouldn't group because if we do we run the risk of the other team getting a penta. The other team though was a well organized machine.
I feel there needs to be some tuning to the matching system because something does not feel right.