Microsoft just dropped support for the
10 year-old Windows 7 and the wailing and gnashing of teeth made the mainstream news... even though the latest Windows 10 (at least the still supported 32 bit version) can still run 16-bit binaries compiled in the 1990s.
If Apple had designed Windows 10 they'd still have had to please a huge, change-averse corporate sector who need their ancient business apps to run without a hitch. MS are still sitting on a backwards-compatibility legacy that stretches back to the 8-bit era.
Even Apple's most conservative pro users are working in fields like video and audio production which can't fall too far behind on technology, c.f. big corporations that still use PCs like a money-saving substitute for 1970s big iron.
If Apple had to please the same user base as Microsoft, Mac OS would still have to actively support classic Mac OS and 68k code and the UI would still be a hotch-potch of Carbon, Cocoa and classic. We'd have two web browsers: modern Safari and an ancient non-standards-based ones for enterprise users... and, yes, we'd probably still have the hangover from an alternate 2007 in which Apple tried to make a single OS for Mac and iPhone, because, as a Microsoft analogue, everybody would have hated them and the only way they could have got people to buy their mobile devices was if they could run the same rubbish-but-industry-standard software as their desktops.
Actually, although it's nice to think that the alternate universe in which the Apple 3 was a raging success would have been a wonderful world of efficient just-works technology that never suffered the pox of the IBM PC, it could also mean that the Mac never happened, everything was still running on some kludged-together monster created by gluing together 256 6502 chips and the graphics standard was still that you had to plot a green pixel next to a cyan pixel to get white because, otherwise, Visicalc wouldn't run....