Yes it is true that the lens is probably the most important part but that really makes no difference as they all, except maybe Fuji have all the lenses you could want.
They all have cheap and expensive ones. Good and excellent ones. Sony is regularly introducing new Zeiss lenses which are world beaters but really are they that much better than Nikon or Canon?
I have an old Pentax DSLR with only 6 MP which has made some great pics. One of the best photographs I have ever made was with a Canon P&S which allowed an extreme close up of a dragon fly. It has 5 megapixels.
I will have to admit that I am probably going to get a full frame 24 MP the next time I get a new one. Nikon also has one with something like 32 Megapixels.
Do any of these modern DSLRs take old Mamiya Sekor lenses?