People complain when every expansion changes the classes. In fact, people are constantly saying they want their class to go back to X expansion when it was the best for them.
Don't get me wrong, I'm onboard with class changes.
But your premise that "people don't get why this is amazing because X" is just arrogant.
I speak only from my perspective. I never been a huge fan of talent system in any game really... i enjoy the first discovery point as I mentioned, but then it kind wanes fast... FOR ME. And you don't need talents to switch up a class mid expansion, you just need to tune numbers differently...
I think you are overestimating how much Blizzard wants to mix up the meta constantly... don't think they want to since all the complaints shows it's not a good thing, even though I personally would like it.