I've been playing piano for over 10 years now and I'm stuck at a point where I don't know how to proceed.
I'm able to play at a pretty intermediate level. By all means, I'm not an expert as I've learned piano myself and only recently started taking lessons, but I can learn new songs really quickly. The problem is that I never get to a point where I can play them perfectly. It doesn't matter how long I pratice something - I get the first 90% in 1-2 days, and then I'm stuck and never improve.
Just as an example - I've made my own rendition of Last Surprise from Persona 5, and after a few days I could play it comfortably. I have been practicing it (especially the hard parts) for over 3 months now, at least 5 times a week. I'm still at the exact same point I was after the first few days. Sometimes I make the same mistakes, sometimes I make mistakes I've never made before, sometimes I completely lose the beat, sometimes I can't coordinate my hands and lag behind... it's something else every single time I play it. No matter how often and how focused I pratice - as soon as I'm trying to play the whole thing from beginning to end I make so many mistakes that I'm really getting frustrated.
Now you might think this is normal if I'm playing songs with difficult parts. But I actually have the exact same problem with easy ones. I've started looking over recordings of beginners and even they are playing stuff better than I am. It's like my ceiling is extremely high, but my floor is just as low as a beginner's. Every single problem I identify and pratice isolated comes back once I actually have to play it in context of the whole song. I honestly feel like I haven't made any progress in the last 5 years at all. I'm just stuck, as if I've reached my full potential, but that's it.
I'm beginning to think that this has nothing to do with my actual ability to play piano, but that there's something wrong in my head. Does anyone have any idea why I keep getting stuck?
TL;DR: I learn new songs pretty quickly, but then get stuck and never improve. What to do?