You make it sound like yearly os updates is a good thing. I completely disagree. Refining and perfecting the stability of whatever the CURRENT os is ... is a LOT more important to many people that a couple new features that a new os may bring. Besides, there's no rule that they have to release a new os to introduce new features anyway - look at night shift, introducted in 10.12.4.
No matter what kind of software we're talking about, forcing a schedule of yearly os updates, come hell or high water (which is what Apple execs now seem to think they need to do) is not going to be a friend to stability. It's common sense.
They should release a new os when it's truly ready ... not when a marketing hack says 'it's time'.