The course I did back in 2015 had a really good focus on the fundamentals; it helped immensely. At some point I also did DAB although I didn't follow it all the way to the end, but it also helped, especially with perspective.
One thing that distract me is the amount of stuff I need to learn as my goal was to learn digital painting. Drawing is very important but it's just the first step, then you have lots of other stuff like values, color, light, composition, etc. So you start to look into these things and there are an obscene amount of material to learn so it gets overwhelming and it put me off every now and then.
I confess that I need to improve my organization skills to be able to go through all that stuff without getting frustrated.