Ah, this is going to be one of those.
Gilded crests drop consistently from content that requires coordination, some level of dps performance optimisation, and difficulty derived from multiple points of failure.
Delves, regardless of their tuning, have none of these three things. I don’t think all three need to be present, but I’d settle for at least one.
Unrelated: PSA: How to ignore forum users with a private profile