As someone who "can draw" by most people's standards, but who never had a formal art education, I benefited a lot from Draw a Box. I liked that it focused so much on the actual, literal mechanics of drawing a good line with your body, which is not something I had ever focused on.
I think it builds sort of slowly, and you need commitment to get through to the part where you're drawing "the rest of the owl" so to speak, aka the fun parts that aren't just endless pages of boxes in perspective.
But, there really isn't a shortcut anyway, and it's worth it, and this course is presented really well, for no money.
Another upvote for Drawabox. Some other commenters here have said things like "Anyone can do decent mark making" and "It's more about seeing than drawing".
Drawabox proved to me that it's a LOT to do with mark making. The difference between a line drawn straight, with confidence, and one that is wobbly and not confident, is huge. It makes a big difference as to the quality of the overall drawing. Just a page of boxes drawn in 3D space, with each line drawn confidently and straight, can look impressive.
I think it builds sort of slowly, and you need commitment to get through to the part where you're drawing "the rest of the owl" so to speak, aka the fun parts that aren't just endless pages of boxes in perspective.
But, there really isn't a shortcut anyway, and it's worth it, and this course is presented really well, for no money.