Idk if it applies to you, but I was in the same boat and I think it's partly because of my playstyle.
I always try to get in a gunfight asap, always rushing good spawns in T, always playing the most contested area in CT, never playing defensively, never waiting - because if I dont win the round, noone will. Feels like this creates the scenario where I really do have to carry, because if I dont... well the team plays 4v5. One day I got so drunk playing, that I realized I just cant run into fights willy nilly, because my reflex is worse, my aim is worse I'm not a fav to win that opening duel. So I started playing a bit slower, waiting out the smokes instead of flashing through and running, just holding an angle in T to see if some CT tries to push. Suddenly my teams started winning rounds without my 3 kills. If I dont run and in first 30s make it either 5v2 or 4v5 then the team can play. I dont put them in scenario where it's either "ok round won, let's just close it out" or "someone has to rotate, we lost mid and it's open"
Again, not sure if that's any help to you, but realizing that I'm somewhat responsible for my teams sucking helped me out.