These are my thoughts and I do not claim that they are necessarily correct. Just think about them and reach your own decision.
I believe Thor:Ragnarok falls into that class of stories I call “mythic.” Such stories start with a character who has a problem, that character gets transported to a fantastic world where they learn some key lesson and return from that fantastic world able to solve their problem. One of my favorite of such stories is The Forbidden Kingdom https://www.youtube.com/watch?v=Hnf3lV_r0oY
The characters in Skarros represent problems in Thor’s real world. They are there to help prepare Thor for the big fight against Hela and to teach him to be a king. So, the real problems aren’t Ragnarok, but what allows Ragnarok to happen; corruption, irresponsbility, cruelty, cowardice, avarice, etc. These are the things which make a story about Skarros actually a story about the end of Asgard.