It's understandable. S2's finale is good but it mostly just serves to set up S3 and the emdgame unlike S1's finale which wraps up a contained arc of S1 pretty well. Great Tree serves to set up the second half of S2 and the escalating tensions of the party, a lot of shit goes down with tangible consequences that are felt the whole way through and into future episodes so it's a lot more satisfying. It's also the first time we've really seen a naive innocent old age Disney Princess archetype really, REALLY fuck up (Intentionally or otherwise) and have to actually deal with the consequences of their actions and realize that shit doesn't automatically get back fine and dandy all the time just because. And that's on top of the new lore we got and a genuinely unsettling depiction of said princess turning into an emotionless and near unstoppable death machine TWICE. And as for Waiting in the Wings, in the Q and A Chris mentions it's his favorite song since it's the culmination of Cass's repressed feelings over a long time and her solo song was always planned from the beginning to be at a pivotal moment of her as a character, they just waited for the right time to use Eden's talent to its fullest.
Overall I'd say Great Tree is a strong contender for the show's best episode.