Middle being the only role with consistent agency turns climbing mid elo into a shit show
This is a major issue, because if you want to consistently have impact over the game without duo queuing, you need to play mid lane.
Jungle is too reliant on all lanes performing well. If your lanes are under-performing or pick champions that don't ever have priority, you get invaded by the enemy jungle and lanes 24/7 and essentially can't play the game, while your ability to secure your secondary win condition (objectives) is 100% tied to your lanes.
ADC is too reliant on the support to perform well. If your support is auto-filled, doesn't know the match up, or picks a champion with no synergy, they can completely throw the lane at level 2, and you spend the rest of the game being dove repeatedly.
Support is too reliant on the ADC to perform well, for the same reason as support, but worse. A good support player can leave the lane and roam if the ADC isn't playing well, but an ADC player is shit out of luck if they're in a losing lane against a hard engage support.
Top is top. By the time it's in a position to do something, the game has already been decided by the other lanes, and the balance in this lane is a total shit show where counter picks dictate your ability to win or lose.
Middle is the only lane that can function on its own. As a result, everyone wants to play it, and you end up getting your secondary role more often than not. This makes it incredibly hard to carry lanes, because no matter what your secondary role is, it doesn't have the same potential as mid lane.
Ideally, jungle should be given back the ability to function without being completely reliant on their team playing well, or top lane should be completely re-balanced so it snowballs less in exchange for having more relevance to the game.
Having to rely on a coin flip to get the role, and then another coin flip on your team mates if you don't win the first coin flip, makes climbing in ranked incredibly frustrating.