WotC released the survey info on this fairly early in 5e, something like 8 years ago IIRC. I can't remember the specific numbers, but at the time homebrew campaigns were more than all the WotC/TSR settings combined (so over 50%). However, I don't necessarily thing that survey is relevant today, so I am not going to bother trying to find it. D&D has added so many new people that it could have easily changed the numbers quite a bit.
I will say that in the 30 years of playing D&D I have never played in an official setting and I have run less than a half-dozen published adventures. However, since 5e I have been buying quite a few adventures, I just don't run them. I steal ideas, encounters, traps, etc. and use them in my setting / adventures instead.