Oldest photo are studio photos (oldest being a tintype, others ... collodion?). Except for the tintype the quality is generally quite nice. Studio lit, static subjects.
Then come the 1920's and a decade of non-studio, candid photos that appear to have been shot on a Brownie-style box camera. These are fairly poor quality. In some cases though they are poorly framed (subjects too far from the camera) and so it is as much the fault of the operator as the poor camera. Photos are exclusively outdoors.
A handful of studio photos are peppered in these decades, now with school graduation photos, maybe a wedding photo shot professionally. These are quite nice. Maybe the nicest of the first 100 years of photos?
Somewhere in the 30's though B&W photos taken on consumer gear begin to appear that are much better in quality. I suspect we've moved past the box-camera and to something more like the folding-style Kodak with better optics. I like this period of candid photos the best — right up until the 40's and 50's.
Suddenly though, mid-Century, the photo collection goes to color, some of them Polaroids. Oh wow the quality falls right off again. We're back to the Brownie box-camera in terms of image sharpness, clarity. I think we, as consumers, traded quality for color and instant processing.
By the time I am old enough to take pictures (70's) I remember using a Kodak Instamatic (135 film?). Also poor. We had flash of course by then so many more photos go indoors.
My mother sometime in the 70's got a Canon AE-1 so 35mm and decent lens (no doubt the kit "nifty 50") make for some of the best amateur photos of the century for our family photos.
It is curious that the pattern would sort of repeat in the 21st Century as I switched to digital. I had access early on to digital cameras (part of my job) so I was an early adopter. When they became affordable I began buying and upgrading through a few lines of nice Canon point-and-shoot cameras. This was the beginning of the "megapixel wars". The quality of the images began to get quite nice — Canon optics, aperture-priority, ability to adjust exposure bias...
And then sadly, the quality regressed since we lazily turned to relaying on the iPhone camera and early on it was worse than that of the nice Canon cameras. (My wife though had graduated to a Canon Rebel around this time and held on to using it for a while so that many of our vacation photos started to surpass those taken with my mother's 35mm.)
As generations of iPhones improved their camera quality, eventually all the Canon gear got left at home since the photo quality of the modern iPhone was "good enough" at last. Playing with lenses, depth of field (no, not the fakey "portrait" kind of computational depth of field) are gone however — I suspect not likely to return. The thinness of the phone means we're not likely ever to see larger apertures where depth of field becomes meaningful.
I started to get into Micro-4/3 for a bit, recently picked up a Sony mirrorless, but I suspect the days of automatically strapping on a dedicated camera when we head out to hike, vacation, are now a thing of the past.
We'll see.