I am (was?) one of those people the OP is talking about. I can listen to something, and just learn to play it. I don't need to know notes. You can play a cover song, and I can tell that you transposed it down a half-step so that your singer can sing it. It is a gift, and it can also be a crutch.
I find it hard to practice the things that most people have to learn to even be able to play an instrument. On the one hand, I don't absolutely need to know them. On the other, I learned that in order to be able to play with other people, you do need to learn notes, keys, chords names, etc. Because of the latter, I've made an effort to try and learn some music theory, where the notes are, the names of chords, etc.
Whether or not the person the Op is referencing wants to learn notes is their decision. It's not a reason to insult them or try and tear them down. In the end, yes, they will probably be limiting themself. Then again, with the technology we have these days, you can be a one-person band and be quite successful.