Another factor to consider could be the oft-undefined "detail". Speaking geometrically:
The OM-1 goes up to 144 lp per mm at the
Nyquist frequency, the Z9 up to a mere 115 lp per mm.
The GFX-100S comes in at 132 lp per mm, which is kind of close to the OM-1 but no cigar.
Of course, several other factors could be mentioned in rebuttal - especially by those who equate MP to resolution ...
... Not to mention factors like lens quality, camera settings, focus, diffraction, tolerance to aliasing, DOF, etc.,
ad naus.