So, to sort of get it back to the thread title.
BCN is a Japanese industry site that tracks the Japanese photo-video sales. Apparently, over there, full frame (both mirrorless and the DSLR) comprises only 10% of units sold and Sony now is the leader in full frame (but they're all tanking).
Makes sense. The amount of human beings on earth that care about the benefits of FF enough to pay the premium for both the body and the generally larger lenses is limited to people who make money with their cameras. Not to mention there are actually crop bodies that I prefer to most FF cameras now (Fuji). Hell for most people the convenience of camera phones outweighs the benefits of having to deal with a dedicated camera at all.
On the stills side I haven’t felt the need to upgrade in a long while because the products are so mature and I’d bet a lot of others feel the same. I’m using a Fuji crop and a FF camera from 2012. If I need better quality I’d go directly to medium format.