It depends on how you set them up, and when you're on smallish tyres with no suspension, small changes to geo are noticeable. Some of the new school gravel bikes (like the Evil) are overkill in my experience. Yes, they're stable at warp speed, but they're also noticeably less agile, especially when you're bunny hopping stuff or changing direction quickly (like you do a lot of when you take your CX / Gravel bike on mtb trails).
This is my favourite personal bike of all time, it was sadly stolen (using a carjack to bend steel bars and doors no less). It was the proto Moots Di2 bike I designed with them way back. The sliding dropouts were less about SS and more because we all knew thru axle disc was coming. There's an image of the bike when it was first built too - hydro wasn't a thing at that point and as has been mentioned above, tyre choices were very limited.
I've just recently had a replacement (not a Moots) built, but it was lost for months in the Covid logistics fiasco. It's turned up, but is in the wrong country and will be a while before I can build.
For me front derailleurs are still irreplaceable on long gravel rides, relatively aggressive geo works best, and comfort is king.
There's something so satisfying about riding inappropriate trails and places on a CX bike.