
This is the main story how are they gonna have some jealousy in their relationship if there is no third party interested in one of them? Besides, Blondie barely appeared yet, and even so the main focus is not him, but his relationship with Yutong and how it affects the main couple. I think it's a pretty good arc about character development, societal issues and whatnot.

i hope this doesnt come off as rude but this is my interpretation so feel free to disagree
For the story to go back to "main story", there has to be something going on as they make it to the day of the accident. It's why we're seeing all of this. The point of the story is that something is different from back then, whether or not Weiyun survives is dependent on these differences. So yeah jealousy arc may not seem like much but it's telling us how weiyun will deal with this in the future, and if it will cause a rift in their relationship. It's giving a possibility that maybe instead of indirectly dying because of Yutong's rejection, he could die of something else. For now, we have to see the characters grow and change and hope these changes are enough to prevent Weiyun from dying.
I've been skipping through the chapter after the pretty blonde dude appeared like pls get on with the main story????