Theory is primarily a documentation of what HAS happened in music. There are a few theories
that began as soon as the music started (I believe this is the case with serialism since it's a mathematical
approach to music). However, just because the music happens before the theory does not mean it is pointless.
In my experience, most cats who refuse to learn theory either (A) are old and already established musicians or
(B) are ridiculously lazy and get put off as soon as they have to learn anything beyond a pentatonic scale
or (even more so) have secondary dominant functions mentioned.
Personally, a cat has to be incredibly good with his ears and have some serious style if I am going to ask
him to play my own music. Otherwise there is no point because a lot of it is either complicated rhythms
or harmonies that are constantly shifting tonalities and it would be unreasonable to sit down and explain
each beat of the chart when theory could easily explain most of it (yeah... most of it, haha).
I would think of it like mathematics. Sure, you learned how to count and maybe that works for you.
However, imagine you are given a task and your boss states, "I need you to count these basses. Each
group has five basses and there are twelve groups. Count 'em up and then play whatever you want."
Here is how each level of knowledge would play out...
Beginner: 1 + 1 + 1 + 1 + 1... etc.
Intermediate: 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5... etc.
Advanced: 5 x 12
You see how much less time there is?
Way less time spent figuring stuff out and more time playing.
If playing music is your goal... I'm pretty sure having the knowledge means
you get to play more music!
Also, if you let theory change your style negatively, you're the only one to blame.
That's like saying, "Ah man... I learned this lick. Now I can never play anything else."
Same with instructors. You find someone you appreciate. You don't have to be their clone.
Keep in mind you are already using instructors since you're learning songs by ear. They're
teaching you their personal vocabulary. That's typically what an instructor does.