This is a funny post. I am entertained.
One thing I would say is: if you think you know a lot about table tennis in theory "and stuff", but your skills don't match your level of theoretical understanding and "stuff" understanding, then maybe the things you know a lot about are not exactly right. There is some stuff in a sport like TT that you only really, actually understand when you can do it. And stuff you think you understand at one level....when you get to a higher level, you look back and think: "oh, I really didn't understand what I was supposed to be trying to do." That kind of thing, especially when someone does think they know, can tend to hold you back from learning what you actually need to sort out in order to improve.
So, an open mind can help.
TT is a very technical sport/game. It takes years for people to be able to accurately read incoming spin and adjust their racket angle, contact point, ability to move, and take a stroke that intercepts the flight of the ball.....etc. The brain processing part of all that which enables people to see what is on the ball and the arc and flight of the ball, so they move to the ball, get there early or in time, take the stroke with the racket adjusted to a useful angle for contact, touch the ball in a way that will work etc, etc..... can take years and years of practice.
If you are on the younger side of things, you will likely learn faster than us older folks.

So, I think you may have that advantage on some of us.