But technically, judging by what few examples I have seen, I think the present generation of instant films (or possibly, the cameras) may still have some catching up to do, compared to the b&w Polaroids of the late 1950s.
SX-70 never (from introduction, to Time-Zero) had the level of crispness and definition that the better peel-apart cameras could produce. This is partly a limitation of how the film works (dye migration through the opacifier layer is certain to introduce a certain amount of unsharpness), and for the cameras that aren't SLR, may also be due to the lens design. The original SX-70 used a front-focusing Tessar -- advertising of the day said this was to allow a deep focus range without requiring a lot of motion (less than a quarter inch for front element, vs. an inch or more for the same lens unit focused) -- which is widely considered inferior to unit focus (which was used for all the peel-apart cameras with rangefinders, at least), but the later non-folding viewfinder cameras mostly used plastic lenses, either meniscus or Periskop style. So none of the cameras were as sharp as they could be, and most of the later ones were less sharp than that.
Most of the 600 family were effectively toy cameras, with even the sonar autofocus replaced by fixed focus (sonar autofocus would have been the last bastion of the Tessar type or even triplet glass lenses in that line).
I don't know that current generation Polaroid films (descended from Impossible) are significantly worse than original 1970s to 2000s vintage integral Polaroids in resolution or sharpness -- there's argument about color rendition and contrast in some circles, but the general softness of the image is a combination of the way the film works and the cameras most available for it.
