They’ve adapted in an evolutionary way for me.
2014: it was about using a CX bike to ride places a skinny tire road bike shouldn't be (or at least we though they shouldn't be), I could go fast, and the gearing was just right for gravel once I made some adjustments.
2015: got a first generation Diverge, which was really just a Spesh Roubaix with clearance for bigger tires and fender mounts, handled way better than the CX, but the tires seemed to be a bit of a limitation (effectively at 32/33mm they were just CX tires), regardless it was a fast bike to ride (I still do use it for my rain bike and commuting).
2018: started riding my full squish MTB on gnarlier trails, and gravel, but the gearing was too damn low and the suspension added a degree of inefficiency that made using a MTB a less than ideal solution. I've glad I never went down the rabbit hole of converting it to a drop bar, and it never fully replaced the Diverge Mk1 that preceded it for the fact it was just too inefficient for me to ride long distances.
2021: full on pandemic and new bike cravings, and the new 3rd gen Diverge is upon us with slacker geometry, longer chain stays, and room for lots of rubber….and like the MTB before, it is 1x11, but with no suspension, it is efficient. I didn't really care for the riding position as originally spec'd, reach to bars was a tad short, and the seat-bar drop was less than I liked, in part due to a 15mm rise on the bars. Swapped in a 10mm longer stem and new (slightly wider, but flat top flared drop) bars, and now it feels right.
Through this process, I've advanced from mechanical disc to full hydro. I've gone from CX geared 2x, to road geared 2x, to 1x. I've never ridden 650b because I've never felt the need for that much rubber, and as my desire for increased rubber has grown, so has the clearance available to me on my bikes. I will never use anything but full hydraulic discs, and I probably won't experiment with 650b, but I'm not adamantly opposed to it. I'm also not married to 1x, in fact I continually ponder going back to 2x on my current rig, just to bring back closer gear steps within the range.
So, what’s the point of that timeline for me? I started out viewing gravel as something to go fast on like pavement…and a gravel bike (whatever that would mean) was a means to access these other surfaces to do that. Over time, my opinion of gravel has not changed much, though how I solve the problem of riding on it has evolved. I don't bike pack or do adventure races, I do ride a lot of gravel with a definite preference for the "smoother" forest roads and two tracks, sprinkling in non-technical single track, and I do some amateur racing in Europe (think: long distances on gravel with lots of elevation).