I read 24-50 books on the art and craft of storytelling every year. Your numbers are way off for sports and writers.

4 hours a day is 28hrs a week 24 with a rest day.

This is dedicated practice, add weight training, dedicated cardio and game days... Professional athletes are waaaay over 20 hrs week.

And elite athletes do two a days for most of their careers so they can do 6-8hrs of dedicated training.

All the best writers and musicians I know are practicing 4hrs a day minimum. Writing does need wrest but it isn't the same as sports.

What the writers you're complaining about need isn't rest days or more reading... It's more training. They write without editing. They go it alone rather than join writing groups. And they don't analyze how to get better.

That's what I've seen.