So similar, in fact, that it led to years of allegations that MS-DOS was a ripoff of Digital Research's intellectual property (see https://en.wikipedia.org/wiki/86-DOS#Intellectual_property_d...).

> one could safely say MS-DOS/PC-DOS only existed in the first place as a "quick and dirty" approximation of CP/M

One could indeed, especially seeing how the original name of the product Microsoft acquired and turned into MS-DOS 1.0 was QDOS, which stood for "Quick and Dirty Operating System" (see https://en.wikipedia.org/wiki/86-DOS)

:-D