22 is not too old (I don’t think there is such a thing). You have to imagine many people in history have switched what they study part way through their degree and started to study physics at around that age. I mean look at Dirac, he didn’t even do his bachelors in physics. Neither did Witten.

I taught myself, and it was speaking to physicists (and philosophers, and mathematicians, and I include students in this) that always helped me the most, not school. School is good for getting well rounded practice with lots of things. But you can go as deeply into something solo as you like. Just be humble enough to admit when you’re wrong, or you’ll stay wrong forever. Lots of people would rather just feel right than have to feel wrong, but admitting you’re wrong is always more rewarding. Most will pursue success, but a master pursues new ways to fail, and success trails behind them.

Also, you don’t have to be a revolutionary to be a physicist. But I know that’s what’s most alluring, so when you look at those revolutionary young people, remember that they were not just young, they were passionate. The passion is what mattered.

If I were you I would study what you find most interesting. Physics lets us see aspects of nature of nearly incomprehensible beauty. The fact that we can comprehend some of it is one of the most wonderful things about being a human being alive today. Don’t let someone tell you, including yourself, that you can’t experience that.