superior due to the narrow-wide chainring
Fully agreed. Narrow-wide rings are absolutely a boon to mountain biking as are derailleur clutches. And 1x is superlative for hard trail riding on that factor alone.
A factor in the issue I take is the proprietary nature of modern bike drivetrains. With older drivetrains, we could mix and match to our hearts' content. But now, even within a component line, e.g. Deore XT or SRAM X[n], specs such as pull rates can be different even for the same cog count. "These are the only combinations of components we think you should use, and we will do everything we can to block you from customizing." Shimano is especially egregious about this expensive mess, and they know it, which is why they tried to un-hash things with CUES.
Pretty much everything 3x9 all works together. Road derailleur and cassette with mountain crank and bar-end shifters? Sure! Gear range for days. I sincerely believe this is to sell more bikes. Want to climb hard pack and mixed surface? You need a gravel bike! Want to get groceries? You need a commuter or loaded tourer! Want to go on a fast road ride? You need a road bike!
It used to be really easy to build up a bike that could perform most bicycle functions well. Mixed-surface, loaded, commuter/grocery-getter, randonneuring, snow, rain, club rides... one bike with maybe a wheel change*. Good luck with that now. Gravel bikes are kinda filling that niche now, but the components and frame manufacturers are again trying to fracture that even further. The gravel drivetrain won't have the range to cover all the use cases without a cassette or crank change.
Moar rant, moar example: my partner works in an LBS. We can literally afford to buy any bicycle we could want. She wants a general-purpose gravel bike, and it's not even a case of "just spend more money to get these additional features." Component selection on a pre-built, geometry, wheel selection... all tightly engineered to cover as few use cases as possible. Okay, we'll build from a naked frame. Oh, the more racy geometry frames lack braze-ons and can't fit a 50mm tire.
*It makes complete sense to have a full-squish mountain bike for the aggressive off-road stuff, and those bikes are necessarily different. Even for that case, I can hang with the LBS trail/flow rides on my do-almost-everything bike. My current do-everything took me more than six months to source compatible parts and troubleshoot. This used to be a matter of just pulling the trigger on the parts I wanted.