I don't think I know a single person who bought a gravel bike that doesn't use it on mixed roads. But I think everyone I know who's done it also just realizes they have done it on their road bike but realize there's more comfort on the gravel bike and aren't concerned about outright speed. Again, it's regional. If you're in Hunterdon County, Western Morris County, etc there's more options for gravel roads. If you're a road rider in Union/Essex/Etc that's probably not an option. Where I am there's limitless gravel roads and the roads are scary AF. I switched to my CX bike for road because the 32mm tires were more comfortable and I stopped riding with other people so a little slower for the same effort wasn't an issue.
I don't really remember CX bikes being hyped and maybe that was just before my time. CX bikes are pretty dumb now unless you actually race cross. I'm really happy with my CX bike and it's probably got more miles on it than any other bike I own and it's extremely versatile but if I had to replace it it wouldn't likely be a CX bike. Or I just wouldn't replace it...
I'm 100% going to say it's still Fat Bikes because there was a multi-year period there where most shops were pushing them hard as the do-everything bike. I bought one for riding in the winter and realized it's a pretty damn specialized bike. 99% of the time I'd rather have a regular mountain bike. The CX bike I can at least comfortably ride into town on. There's a few people that are all-in on fat bikes but in reality it's a really small niche market now with maybe some outlying areas like people that live in Montana or just riding on the beach or something. Well, and electric fat bikes, for whatever reason I see those on the bike path relatively often ridden by older people.
I do remember reading an article about a bike shop owner in the UK saying all his urban bike sales were now fat bikes as everyone wants a "burly looking" bike for riding around casually. I guess like the urban bicycle version of the Jeep?
