Any talk about feature walls always brings to mind back in the mid-1950's when my Dad offered to decorate my bedroom as I wished it for my 16th birthday,. Also had a new bedroom suite then. DIY decorating was still pretty new, and was nowhere near as simple as it is today. Much wallpaper still required all the edging cut away, and wallpaper paste was different to what we have today,.
Anyway, I spent a long time working out what I wanted in that bedroom. The wall opposite the door had two small windows, and I decided to have that in a different wallpaper to the other three walls. Then to have curtains in the colour of the other 3 walls there and a large piece of curtaining to cover my divan bed, which I could move flush against that wall - giving it the appearance of what we now call a 'day bed'.
Well, my father was furious when I told him I wanted one wall decorated with a different paper to the other three - accused me of trying to make a fool of him. Arguement continued for some weeks, finally got him into wallpaper shop to talk to man there who told him that this was the new modern way. I did get it done with my 'feature wall', but Dad never actually confessed that he thought it looked good.
In my old house in London I made the chimney breast in the through lounge the feature wall. also in my bedroom had the wall behind the bed painted blue and the other walls all white.
Some rooms do lend themselves to this sort of feature, others do not. Am spending quite a lot of time considering how to decorate the bedrooms in my new flat and Living room. Will not have a feature wall in the Living room, it is a quirky shape so does not lend itself to that.
TBH - does not matter what is/what is not in fashion, it is down to those living in the rooms and what they like that matters,.