It's not your teammates it's your attitude
I want to start off with two facts 1. I'm not good at Marvel Rivals with a peak of Plat 3. 2. I was a longtime Overwatch player with a peak of Masters so I've been decent before.
Let's take a very typical example of a bad match of Marvel Rivals. You're team is 1 tank 4 DPS and 1 healer. Immediate in-fighting due to a poor team comp leads to the team not playing together for the first fight. Inevitably after the first half or first point etc someone is doing the worst and they get blamed. This causes that person to play worse in most scenarios (by either getting self conscious and swapping to a role just to fill or by getting angry and being overaggressive). The game ends in a loss. Everyone blames someone for the loss gg go next.
There are a lot of aspects we could dive into but first let's look at why this all started.
Everyone has a preconceived notion of the best way to play. What characters are good and bad, good team comps and what are the metrics of doing well.
Now let's take a detour and I promise it'll make sense.
You've probably played chess at least at some point in your life. If you played against against Magnus Carlson you would almost certainly lose.
Why is that? You have a winning position (heroes). Assuming this person at least knows how to play chess Magnus doesn't know any rules that the you don't.
Why because you aren't good at chess. So stop thinking you know everything about Marvel Rivals.
No one has mastered this game yet. There is always more to learn, more to figure out. Stop assuming you know best. Stop assuming because you aren't playing meta that you are going to lose.
Let's look at another misconception in the example:
You don't have the deep understanding of the game to understand who is even at fault. Was it really the DPS doing bad? Or did he have no space to be able to shoot down the iron man killing everyone. Maybe the support had 50K healing but never looked left or right to heal a DPS. Maybe the tank really was making space but no one followed in with him causing him to die.
Who knows? Stop assuming you do.
Last misconception I'll tackle: Not everyone is playing the game for the same reason you are. People play the game for generically three main reasons: 1. To have fun 2. To get better at the game 3. To win
Sometimes you can play for 2 of the three reasons but you have to figure out what those are. If you only want to win then find a group who wants to win. Play with like minded people or accept that sometimes your teammates don't agree.
If you play to have fun then don't let someone else ruin it for you. Mute comms or play with friends. You can still flex and have fun on another role. Running in as Cap or sniping people with Luna snow is also fun.
If you play to get better then see those bad games as a way to get better. Practice something. If you are a DPS but can't get heals play a dive DPS. If you are a tank practice taking space. If you are a support practice shot calling even if no one listens to you.