It's not true that early versions relied on printing because most people didn't have monitors. A teletype wasn't all that much cheaper than a keyboard + display interface, and monitors were standard on the S-100 and adjacent systems that were around in the late 70s and early 80s.

CP/M was a super stripped-down clone of the basics of DEC's TOPS-10 mainframe OS, and many of the commands are directly comparable.

If MS-DOS hadn't happened, and if Gary Kildall had been a smarter businessman the world would have run on CP/M, and especially the PC compatible CP/M 86. DRI's products soon sprouted concurrency and multitasking while MS was still trying to work out how to manage memory, so Kildall's failure may well have set the entire industry back by between five and ten years.

DRI also had the GEM windowing OS - as seen on the Atari ST - which could have given PCs a graphical OS, possibly with multitasking features, long before Windows became a serious thing.