In article ,
wrote:

Seems to me that FF is all about connectng back to the old 35 mm film
format, and very little else, since smaller sensors with the same
pixcel count in conjunction with shorter lenses could do the same
thing, BUT smaller and lighter. What part have I got wrong ?

just about everything.

full frame sensors produce images with higher image quality, lower
noise, wider dynamic range and/or higher resolution, and the lenses
aren't necessarily bigger.

so no, a crop sensor can't 'do the same thing'.

some people might not notice or care, but that's something else
entirely.