The unfairness on this chess app is insane


It's to keep you from achieving the rating you deserve.

Anyway, it's up to you if you don't want to play anyone rated much higher. It's in Settings > Gameplay.

settings > gameplay
Then choose the range you want, for challenges you make and challenges you receive, for example -400 to +400 compared to your rating.

You choose the range of your opponents ratings. When you start a game, it will only match you within that range.
If you're rated 750 and choose a range of -250 to +250, you will only get opponents rated 500 to 1000.

Go to the "Play" menu.
Here, choose "Custom", and here you can choose how much upper can the rating of your opponents be.