I'd go as far to say Heavensward may be the benchmark for whether people will enjoy the rest of the game. It's where the voice acting and general presentation upgrades to a level that, to me, remained consistent throughout the rest of the MSQ. Particularly important to me is you get to see strong examples of how their narrative structure may or may not work for you.
Specifically, there's a point where a major event gets walked back really hard, going from "this changes the world!" to "oh nvm everybody's fine don't panic". This is not a bad thing by itself, the devs ultimately want their story to be mostly positive and uplifting, but given people hyped up how "dark" the game gets I was left quite dissapointed on that front.
I had to learn more about it after that short clip and found an overview page which is fun to read if your browser can translate it: https://www.dentsubo.net/circle/spe256.html