I clicked on this topic because it's an issue I sympathize with. I'm not currently able to take on piano lessons, and I sometimes worry that my playing has plateaued--or at the very least shifted from making significant strides to smaller ones verging on intangible.
That said, I don't think the sentiment should be: "there's something wrong with me!" (or the related but less strong sentiment "I've reached my natural limit." Doing so might assume that you know the right way of going about things, that you execute them all in a proper way, etc. and can clearly determine based on your knowledge that there is no way forward. Instead what I try to do is to be humble. Assume that there are aspects of my playing and practicing that escape my notice. And realize that stumbling blocks with playing can sometimes be caused by major issues (tension) or lack of foundational skill-building.
These stumbling blocks often need to be addressed, and the result isn't always a quick fix. Often you have to regress in order to progress. I did this myself. I was at a level where I was starting very difficult works, but my hands were riddled with tension, which was making my playing rough. So I basically started from scratch--no more difficult works, no more scales at 144 bpm or above, no more trying arpeggios at max speed. It was hard to do, because I had been learning things that had been really aspirational to me. But instead I focused on being as tension free as possible and also on always aiming to achieve the exact sound I wanted. My playing was so slow I couldn't play the opening movement of Mozart's K545 anymore at speed. But when I played the limited things I did were smoother. My thumbs didn't cause little accents on arpeggios. The rhythmic evenness of my scales improved. I was more in charge of the tone I was producing. It took a lot of humbleness to admit that I was doing something wrong, and that I had to simplify everything and prioritize things I had never previously considered. Only just now I'm learning my first allegro piece (a page long) in a year and a half (and I'm doing it very cautiously and mindfully, starting at half speed and ensuring that my hands and wrists stay loose).
Due to the issues you seem to have, there probably isn't going to a be a simple "try this easy trick to get fast arpeggios" solution. You might have things to undo in order to get there. And sometimes the solution is going back down to basics in order to ensure your entire playing mechanism is approaching things in a relaxed and efficient way (if it's not, your entire playing mechanism, hands, wrists, forearms, shoulders, etc. can go through a chain reaction of overcompensations that will in fact give you a speed limit and likely cause you to lose control of your sound at higher tempi). If you can play things fast at a stationary hand position, you could be able to do so with changes of hand placement, but it requires the right kind of practice (and not rushing or pressing to do too much too soon).
So instead of bemoaning the impossibility of advancing, I would suggest you approach your own playing critically--not that you're saying "I can't do this," but rather that there are likely things that may pass unnoticed by you that can hinder your playing. Instead of pressing or doggedly repeating a problematic section by clicking up the metronome each day, I'd suggest you play it slow, ensuring you're relaxed, and at a tempo where you can control the sound at any dynamic or articulation. Get comfortable with arpeggios in general, really listen to the sound you're producing with them to locate problem spots or inconsistencies, be sensitive to the way your hand feels and what doesn't feel easy. Because fast playing if it works is governed by suppleness and not strain. With what you're working on, you're doing something new--and it's a good idea to approach things that are new with attention and care to your technique and relaxation, which might make the learning curve initially steeper but serve you better long term, as you'll be able to more easily and with less strain approach analogous figurations.
Topic: Is there a time you accept you cannot advance to a higher level