It's partly that the structure itself feels sort of inorganic and forced for a fantasy setting to me (progressing through leagues with divisional rankings, pre-season -> season -> playoffs).
But for a few quick, high ROI things that could be changed: Pre-season/season could use a rename. Narratively, maybe some months have harsh conditions so the guilds spend them preparing for when adventuring is more fruitful. "Divisions" and "leagues" feel very sportsy and could probably be reskinned without a big lift.
A few things that took me out but are more of a lift and might not align with your vision for the game: Having the division/league progression built around trials that every guild attempts feels sort of artificial to me, like the purpose of adventuring/attempting dungeons is to earn points, rather than points being an abstraction of a more natural purpose. Conversely, the delve rating as a tie-breaker abstracts things that would feel more natural as mechanical consequences - eg: clearing dungeons less efficiently/with more casualties leaving you with decreased capacity for future dungeons and making it easier to fall behind other guilds.