I agree. I don't know that skill growth can be provided by "mentorship". At most, I think mentorship can provide (or is perhaps conflated with providing) direction & guidance.

I've never been in the situation where someone can magically grow my skills for me, or download information into my brain for me.

Sure, there's exposure to ideas regarding programming frameworks, ways of doing things, system design ideas to receive from colleagues & supervisors. And communication & leadership knowledge & experience gained as well.