Quality usually don't go up when releasing less frequently, quite the opposite. The more you change things, the more likely you are to have severe bugs. When Apple was releasing major OS upgrades less frequently, you usually had to wait until a .4 or .5 point upgrade to have something usable.
The first release of macOS Sierra (10.12.0) was vastly more usable than the first release of MacOS X Snow Leopard (10.6.0). I should know: I transitioned to Snow Leopard on release and practically nothing was running on it. I think it's the only time in my life I reverted to the previous version of macOS... It didn't prevent Snow Leopard to become one of the best OS, in the end.
The problem is that Apple is shipping things that aren't right/ready, but this should be independent from the release schedule.