It's not that you can't, it's just that there's nuances you might miss if you don't see it in action. Theory vs application. And for some of us, exploring different game mechanics is part of the draw of the hobby. IF you have the interest and IF you have the time, playing other systems can greatly expand your understanding of the hobby as a whole.
If all you want to do is be a sculptor, sure, skip the painting classes. But you might miss out on something you didn't know you found fun.
I could also miss out on something because I spent time playing that other game. We all make decisions on how to spend our time, what will be valuable. For example I will never drive a semi, but I did take a race driving course that cemented best practices for me and gave me techniques for dealing with emergency situation handling. I am a better driver because of that course. I cannot see how learning how to drive a semi could have been more useful. It's the same with games. Playing a different game and playing it for long enough to really understand those subtleties would take at a guess 50 hours between getting up to speed on the rules and actually playing a short campaign. For one game. I can't imagine how many blogs, books, conversations with fellow gamers can happen with those same amount of hours all of which can be done on my schedule. Even if it's something like 20 hours to really get to know a game, that's still a huge commitment of time and in many cases money.
If you enjoy and have the opportunity and time to play other games, great. I don't. Could I hypothetically learn something new? Anything is possible. But I can get far more bang for my buck (and time) pursuing other options.