A mix of three.
I used to do a lot of adventures from scratch - mostly because I liked to, but I had a couple of folks in my old group that had read/played the standard printed adventures, so I couldn't use them straight up.
I've also run several published adventures, either fully or in part. A couple I've run more than once for different groups (noteably, Ravenloft and White Plume Mountain).
Finally, I've also taken pieces - encounters, rooms, monsters, traps and either used them for springboards for my own custom adventures or put them in as-is in a custom adventure (example, using the Chess puzzle from Ghost Tower of Inveress as is in another trap dungeon, or being inspired by GDQ to make my own adventure to pit the characters against a giant-drow slaving ring).
For most of 5E though, I've used premade adventures - I just didn't have the time, nor was I willing to battle with getting familiar enough to make my own. Though here lately I've learned enough (yet again) to starting to devise my own content once again.