I don't think collecting the refs was a waste of time.
As someone who hasn't done classical "studying" of art for like years, I can safely say that all things you look at, if you're really paying attention is a form of passive studying. The brain is always processing things when you don't realize it. That's why drawing every day actually works as a form of improving what your brain knows. IT's also why just looking and observing other images, good content, etc also helps you improve. But it's so small and in the background it doesn't feel like you've learned something 'major.' Even so it adds up.
But when it comes to improving at something you don't know, That's where deliberate practice comes in. Deliberate Practice is a good thing to look into a as method of improving at some specific thing ; as opposed to repetitive practice, which can be mindless repetition and not very directed at a goal of improving something specific; often it's just vaguely about 'getting better'.
Imo, all studying is is defining where you are ignorant then going out to learn what you know you don't know--and in so doing find out more of what you don't know, and so on. Sometimes you have to re-learn how to study or change the way you study, and that's all part of the process too.
The way I see it, 'spending time on things that will make you better' is just honing in on what you don't do well and going out to find resources that teach that particular thing. Outside of schooling, the way to learn is haphazard with lots of dead ends, weird leaps, and a TON of experimentation that can feel like a waste of time but you end up learning from it anyway if it's done in earnest. You're in charge basically of your own curriculum.
And of course there comes a point where you have to get out of study mode and just finish creating the thing you intended to create because isn't that what the practice and study is for? I still believe you do just get better at drawing...by drawing, focused study or not.
It's probably not a useful answer, but as indie creators we really are responsible for figuring out the best way for ourselves. What worked for me is Deliberate Practice, which is systematic and purposeful and has the kind of structure I personally need to stay focused. My goals were never just 'get better at art' it was usually "get better at drawing the muscles of the back and nothing else today". Break to pieces, then put it back together. Then put that all to the side and create something, finish it, THEN do some study to fill in areas I lacked.