Hi Sarah,
Welcome!
In my opinion it depends what you define as good.
Can you learn a level 4 song on this site without understanding the theory behind it. Yes. If you define this as good then there is your answer.
Can you understand the required tonal changes to play in D Dorian (both in chords and scale) without any music theory.. Probably not. If you define this as good then you’ll probably going to need some theory.
So I guess it depends on where you want to go.. for me personally learning theory allows you to create/improvise which for me is where you can both lose yourself and find yourself in the music all at once 🕶