I finally gave up on using regular drywall screws for everything after a ceiling patch fell down.
For years, I thought a drywall screw was a drywall screw, and I'd grab whatever was cheapest at the hardware store for any job. That changed when I patched a small hole in my kitchen ceiling with some generic screws I had lying around. About a month later, the whole patch just dropped out, taking a chunk of the old ceiling with it. A contractor friend came over, picked up one of my screws, and said, 'Paul, this is for hanging pictures, not holding up drywall. You need coarse-thread for wood studs and fine-thread for metal.' I felt like an idiot. I went back and bought a box of proper coarse-thread screws for a few bucks more, redid the patch, and it's been solid for over six months now. It's a tiny detail that makes a huge difference in holding power. Has anyone else had a project fail because of the wrong type of screw?
Went with some basic drywall screws from the hardware store. They were cheap and got the job done for hanging that shelf. Honestly, I was just glad I didn't strip the heads like last time. That project was fighting me the whole way.
Yeah drywall screws can work in a pinch but I read they're actually pretty brittle for holding weight long term. They're meant for just drywall to metal studs, not wood. I switched to basic wood screws or even deck screws for shelves. The threads are different and they don't snap as easy if something shifts.