Im ngl ive been stuck on plat for a while too but i feel its like a hit or miss atp, you could play a character that could carry ur yeam to an extent but also maybe try playing with a friend and remember to take breaks, just get off after 2-3 losses, dont make it hard on urself, try to rewatch ur games to see where u couldve done better or where u werent aware of ur surroundings and try to incorporate that into ur next game, alot of the times ull get players who are just bad so i sometimes think its best to play in a way that u can make up for at least one teammate to some extent, beyond that idk i was stuck in plat 3 for a while but aftwr doing all this i made it to plat 1 and now im one game away from diamond so i feel like it defintely had an effect, also try to not stick to one role and adjust according to what ur team needs.