I would guess the 'agnostic' designation includes a lot of folks who grew in some religious doctrinal system, reached a point (for a wide variety of reasons) where they no longer accept any of the received doctrine, but still have the sense that they don't understand existence at any fundamental level and are left in a state of irresolution. I think that's quite a bit different from a person who has come to a positively objectivist view that nothing they can't see can exist.
I think the big shift in the works is that as attendance at Churhes fall, fewer people are getting that doctrinal education in the first place and their agnosticism is even more ...diffuse (for lack of better word). 🕉️