First of all, the old 105/2.4 P67 lens I own is ridiculously sharp. The complaints that come up about these things have a different source, I suspect.
For one thing, people confuse it with depth of field problems. They either stop the lens down to the point of conspicuous diffraction or erroneously
think wide-angle lenses are inherently sharper. No way around that dilemma except to use a view camera with plane of focus tilts, or something
comparable. Second, they don't adequately appreciate the real weakness in the P67 system, which is the mirror slap at slower speeds, which is what
the mirror-lockup is for, which obviously mandates tripod usage. Third, people run around with these silly tripods that look like a three-legged selfie
stick with a wobbly ballhead that would make even an aphid seasick like a drunken sailor. The problem only gets worse with long heavy telephotos,
where a serious tripod just comes with the territory. But still, with the right lens choice, this is a handholdable system, once popular with aerial photographers, fashion photographers, and once even available with an underwater housing. The 75/2.8 would be an excellent choice for handheld work, though I personally prefer the 75/4.5 on tripod. But from an engineering standpoint, of course a better wide-angle lens can hypothetically be made, because you don't have that mirror distance in-between to contend with. Yet if I compare prints from my humble affordable P67 75/4.5 to my
friend's taken with Zeiss 66 lenses that cost ten times as much (and we both use 105 Apo Rodagon N's to print em), it would be damn near impossible
to tell them apart from a sharpness basis, and I think I prefer the subtle bokeh quality of the Pentax better. This is more of a fun argument overall.
Most pro MF systems were very well designed to begin with. Just depends on you priorities focal-length wise, weight and budget issues, etc.