>> Native talent is definitely a thing and anyone who says otherwise is either lying or trying to sell you something.
Maybe it is a thing. But I doubt it's the most important thing.
I'm an amateur musician too (I think that's what you mean by part-time?). Yep, I've seen people with a native ability, who can just grab an instrument and play. At the same time, I've seen the same people never improve no matter how much they tried, mostly though because they never tried, while others who were not as "talented" spent the hours and got better and better and better, and eventually better than the talented person and then much better than that. Some of the talented persons are too talented for their own good and never figure out what "discipline" means, so their talent remains for ever precocious.
And I've also seen people get mightily impressed by others' talent and overlook their own abiilties, to the point that they severely underestimate them. I have a close example (not me!) of someone who is just good with theory, but gets awfully disappointed that she can't just sit at a piano and start playing without thinking about what she's doing, like a cousin and an aunt of hers do. On the other hand, when I play with her, she's always the one who figures out where a song should start from, how we should transport a melody to our respective instruments, and so on. She knows music. But she can't just "grab an instrument and play" so she thinks she doesn't have a talent. Well I can grab an instrument and just play, apparently, but I have no fucking idea what I'm playing (she usually is the one who figures it out for me).
I digress. My point is this. You observe a person who has a natural talent and a person who doesn't, at the start of their careers. At that point, you can not predict which of the two is going to be a master of their craft, sport, art, etc (or if both are, or neither). There are so many other factors involved that talent, on its own, means nothing.