Yes eno, I think your experience speaks to the balance of quality vs quantity question.
Regarding composition, I've found a great resource for beginning to get a handle on composition and some theory: The Art of Composing, Jon Brantingham https://www.artofcomposing.com/
. Easy to listen to podcasts, blogs or however you like to consume. And inspiring. I doubt I will ever compose anything of much value, but the process intrigues me, and the theory helps my playing and memory.
I appreciate the time limitations. I stopped playing for 35 years due to these limitations. Although I regret that, I'm not sure sticking with it only to do 25 minutes 3 days a week would have been very productive either. As I alluded above, it takes short term commitments and a long term view.
Your comment also makes another point about the kind of "deliberate practice" needed to accomplish the goals of the 10,000 hour idea. Practice requires knowing what the problems or challenges are, and how to fix them. In the past, this was only available through either trial and error (bad way) or with a good teacher. I think this is still true, but we have a lot of other options now too: online lessons, youtube performances, many method books and CDs, etc. The challenge now is, as Jon Brantingham puts it, "information overwhelm".
All this time I thought I was making music; it was making me.
2015 Steve Ganz "Solidarity"
1980 Dauphin D30
1962 Fender pre-CBS P-Bass
National Triolian Uke ca.1930
Almost as many fly rods as guitars