Skill distribution broken?

You won't do anything. This is normal in the "new continuous matchmaking". You have to compete with the best and enjoy the game that way. The problem is that a large part of the "best" are simply cheaters.

This game is becoming more and more visible day by day how it has been dominated by 3stacks, streamers and cheaters.

Solo Q has never been as bad as this and last season.

No offense, but in solo queue I usually have teammates with such stats, but usually we are killed by a full 3stack (each with several dozen kills on one character + best badges, sometimes master/pred badge).

This is fair matchmaking according to EA/Respawn. It is getting worse by the day, because for almost a month and a half on Steam alone there are on average 40 thousand players less. This is very very very much. I don't know how the hell you're in this part of the lobby, but I do know one thing - this matchmaking doesn't serve anyone except very skilled 3stacks and cheaters. The entire lobby is usually wiped out by 1 powerful team that you can't do anything to.

Then you die and repeat the same thing until you manage to win one game 50 or 100 times, and then matchmaking will torture you again for another 50 or 100 games in a lobby where you can't do much.

I don't know what happened to this game and at what point it fell into such a mess, but it probably won't get out of it. Too many mistakes, too many bad changes, too little has been done to combat the cheaters who have dominated the game for several seasons now.

I can attest to the fact that Respawn's skill assessment tool is kinda all over the place. I've seen mine swing 30% of the way across the curve in a single day, and then swing back again the next. I'm not saying that either placement for me is completely wrong, but I am saying that the algorithm must necessarily have a very narrow definition of "skill" in order for mine to swing that far that fast. And the truth is probably in the middle, as it so often is.

In your case you have to do the impossible, which is to separate your subject feeling of inadequacy from your actual performance. Subjectively there is no way the game can put any normal human in diamond/master lobbies and have them come out feeling like they own the game. On the other hand, look carefully at your career k/d, win rate, average damage/match, and even average placement (not just the numbers from the current season). If any of those numbers are maintaining above average, or even at average, then the lobbies you're in are probably the ones you ought to be in even if they feel terrible.