Sensors keep improving
and that includes those smaller than FF. But as with film cameras resolution generally improves with a larger sensor (or neg). With most folks never enlarging an image larger than a computer screen
that FF advantage might be less nowadays. DOF is affected and potential large aperture bokeh reduced with small sensors but a smaller sensor also allows the body "and" the lenses to be smaller
and lighter. For this reason I now rarely travel with my full framer. My Sony RX-10 (1 and a III) and an RX-100 are so much easier to travel (or hike) with. So I've lost ultrawide (widest for those RX
cameras is 24mm equivalent) and gained portability. I don't think small sensor wide angle lenses can match the capabilities of FF wide angle lenses. An example would be my Sigma 12-24 rectilinear full frame
lens (Minolta-Sony mount) on my FF Sony or Maxxum 9. Insanely wide yet very rectilinear. I haven't kept up with new small sensor lens offerings but I don't think there are any that can match that.
My Leica 15mm (R) is slightly more rectilinear but its not as wide as the 12-24... and just a tad more pricey (haha!). One thing that hasn't changed with photography is that there is a time and a place for various photographic
tools. I never would have guessed that phone cameras would be as good as they are now but they are not cameras and one of the main reasons is sensor size... but their images look darn good on a small
screen. No match for a good 1" sensor camera and the smaller RX cameras (along with 1" sensor cameras from other manufacturers) are as pocketable as a phone. You just can't text, talk or surf the net with them.
ALL the electronics in them are dedicated to producing a great image while allowing total control of settings. Given the advances in miniaturization I'm suprised no one has tried to put a camera in a watch!