But I’ve also worked with photographers who have become successful pros within a couple of years of starting.
The difference is largely down to attitude, btw I have owned a guitar for 15 years, and it gives me no pleasure at all, I still can’t play and I’m certain it’s not because I’m incapable, more that I can’t be arsed.
It's a good comparison, as you need tremendous effort and enthusiasm to become a good musician. On the few occasions when I have gone to lessons to play a musical instrument, I was expected to practice at least an hour a day, plus at least one "big" session a week of practise, and at least one session a week playing with others. Fortunately, this was far too much effort for me, so the world has largely managed to avoid my guitar, clarinet and bagpipe playing !
I think, the problem (and the joy) with photography, is that the "cost of entry" is so low (in terms of effort). It's just too easy to start producing pictures without fully realising just how difficult it is, and never learn how much effort and enthusiasm is needed. This is in contrast to your guitar playing, or, for example, painting, where playing a recognisable tune or drawing a recognisable picture of your granny is difficult, By the time you have have learnt the discipline needed to learn the basic skills of being a musician or a painter you have also become skilled in the "discipline" needed to become an "artist".
Ansel Adams, spoke about how important the discipline learnt while training as a concert pianist was to his photography, and Cartier Bresson spoke about how essential it is to practice your photography every day.
And while not comparing myself to either of the above, I find a big difference in my relationship to photography when I've been taking photographs on 20-25 days of the month compared to the months where I've only managed out 5-7 days.
With the high effort months I get into a "flow" and both the technical and creative elements just come more naturally, and with less conscious effort. I really enjoy my high effort months.
As an aside, it;s interesting that it's only during the "low effort" months that I contemplate replacing ny D750 with a Z7, during the "high effort" months it never comes into my mind.