I definitely land mostly on the 'took lessons/studied/got a degree' side of this. Like a lot of people, I started drawing when I was a little kid, and my parents were supportive enough to let me take all sorts of classes through the parks and rec district, Saturday Academy (once), and other stuff. People bought me art books for Christmas, birthdays, etc. In school, I took art classes whenever I could for electives.
In college, I majored in fine art, fully intending to go into comics. When I graduated, went to my first convention, and got a closer look at the comics industry, I decided against it. I then worked at an art supply store for 6 years instead, which actually taught me a LOT about the materials themselves, much of which none of my classes ever really got into. Over those years, I used/was reasonably familiar with how to use probably 75-80% of what was in that store. (Strongly recommend working at a good art store for a while for any aspiring traditional artists, if possible.)
I still have art books, I still occasionally watch tutorials online, I've even taught art classes, but it's been a long time since I've taken an actual class. Sometimes I kind of want to.
There's an element of my work that IS entirely self-taught, though: the markers. I've never had a class discuss markers. I've never owned an art book that explained how to use them. I've never seen a tutorial online that showed me any techniques I didn't already know. I've considered writing a how-to-markers book before, but it didn't seem like there'd be much demand for one.
(Funny story, for half a semester, I decided I'd do graphic design instead of fine art. So I go to my first graphic design class, which was computer programming or something, the professor says the word 'algorithm', I say 'nope!' because math and I are NOT friends, and I change my major back to fine art ASAP. My painting professor, on having me back in one of his classes, said "Welcome back from the dark side.")