TL;DR What people remember fondly is not Mac OS X 10.6.0, which was in fact very buggy, and buggier than 10.5.8, but rather later versions of Snow Leopard after almost 2 full years of bug fixes.
See also "Snow Leopard bug deletes all user data": https://www.reuters.com/article/lifestyle/snow-leopard-bug-d...
The yearly release cycle is the problem. Apple needs "another Snow Leopard" only in the sense that I mentioned above, "almost 2 full years of bug fixes", although at this point, Apple has more than 2 years of technical debt.