I still feel though that increased chain line and therefore less longevity to drivetrains HAVE to be an issue or factor over the long term, and as mentioned, for touring and easy paced riding, shifting fd's is by no means a hardship or have any downside. Racing mountain biking or cyclocross is one thing, but for all of us doing touring and such, a single chainring really doesnt have any advantages at all compared to the positives.
I definitely wouldn't go so far as to say there were no advantages. It is one less cable, one less shifter, one less derailleur and one less chain ring. That equals less parts to maintain, less things to fail, a bit less weight, pretty much no chance of shifting off of the front ring, and so on. I kind of like the simplicity. It isn't much of a big deal, but I also prefer to go lighter when there isn't a penalty for doing so. Whether any of that is important to any given rider is another matter, so like most things it isn't a slam dunk, but rather a personal preference choice. I'd lean that direction if I were buying a gravel bike today even if it were to be my touring bike.
I realized that I would be happy with a 1x after having owned a 2x11 mountain bike for a while, riding it extensively, and realizing that the double was kind of overkill. I think for an adventure/gravel/do-everything bike that would be even more true.