The whole “growth mindset” thing feels like a bit of a flawed idea as well to me. It does sound too much like “if Elon Musk can do it, you can do it to, you just need to work harder”. It sounds very much like something you’d say to an underpaid gig economy worker to keep them going, doesn’t it?
As usual, just because A is wrong, it doesn’t mean the polar opposite of A is necessarily right. Most of the time A is wrong just because it’s an incomplete picture of a much more complex phenomen, which can’t just be boiled down to one statement. In this case A is not wrong but merely inaccurate.
So saying that everything is either something you can do or not based on innate abilities, is of course highly inaccurate. This doesn’t mean there aren’t such things as innate abilities and that these do not influence how your life will develop, the choices you will make and the possibilities to which life will expose you or not. Of course this also doesn’t mean that you don’t have to work hard.
Somebody once said this (sorry I can’t remember who): when you achieve something over time there’s basically three main factors at play: inborn abilities and family, luck and working hard.
You usually need at least 2 of these to achieve something.
Apart from Inborn abilities how you grow up and where can have a big impact, being born rich can help a lot with certain careers it seems. Luck could play a big role, but you can only be lucky if you work on exposing yourself to luck 
If we consider somebody talented it’s sometimes because they have achieved something in music. It may be because they made a big breakthrough, or maybe just because they are being praised by many people.
In reality they might not be much more talented than we are, maybe they just were a bit more lucky, or they had a rich family, happened to be into a style of music that in/was fashionable or they were just more socially apt. Or maybe they really just worked harder to get there. Who knows. Fact is, it can be misleading to compare onself to other people.
This said, I don’t think there is nothing wrong with being content of what one has. It’s a beautiful thing. Playing an instrument, no matter how you perceive it, good or bad, and finding joy in it, is a beautiful thing. I also think that one can do that and still strive for more. Actually finding the balance there is probably a very important thing. Because to me the best way to work on ones skills is to do it with joy.