[personZ]

Cartier-Bresson's "Man Leaping" could not have been captured with a cell phone camera. The shutter lag is just too bad.

Humorously, he didn't even see the man leaping, and wasn't timing for that. He took some shots, and it turned out to be a keeper. Such is exactly the nature of smartphone shots, as an aside -- people take countless shots, and among them some gems appear.

for millions upon millions of historic and sentimental potential pictures

This is where your argument falls apart. A modern smartphone has better image capture than SLRs -- top of the line SLRs --from just ten years ago. Despite your focus on shutter lag (where you can prefocus/expose on a smartphone just like an SLR, and then have a close to instant shutter), the shutter lag on current smartphones is, again, similar to top of the line SLRs of a few years ago.

With a large sensor and lenses, at any given time you'll always yield a better result (presuming you assume that such is always available when the moment arises). However at the core of photography, the technical side is far less important than it is held to be, and if we really need to bring up history, a modern smartphone was better than what the most committed photographer had in their arsenal not that long ago.