Is 400 ranking so dumb under average?

Learn basic chess principles like king safety, piece development and moving with a purpose. Learn basic tactics such as forks, skewers, discovered attacks and pins. Knowing the rules is not enough, you really have to study the game to be good. If you lose to the Scholar's Mate then you have not studied the game, it is literally the oldest trick in the book. The f7 square is the weakest, so if you are playing as Black make sure nothing can attack that square in the opening.
I didnt feel this stupid for a long time.
I know the rules of chess for a long time, but started playing here regularly this year.
In everything in life I am slightly above average... not a genius level but slightly above avg at least.
In chess, I am so humbled, ego eaten, smashed... and full of frustration.
First, is rank 400 really not beating 90% of beginners?
and secondly, my short term memory, I realized I have a terrible problem. Even when I want to focus on counting captures how many protect what... I have very hard time to focus or memorize.
As I finished writing this, I realize there is no point in trying chees until memory issue is solved. I must have an effective short term memory for good chess.
Thank you!