We were all a part of it. Myself included.
So... Ezri?
A better Dax?
Making the best of a bad situation?
Or a mistake that just shouldn't have been made?
If there were no real-world considerations I would have liked to have seen a male Dax in S7, as I feel that would have made the character dynamics a bit more interesting and potentially progressive.
I wasn't prepared for Dax to change hosts between S6 and S7, but in retrospect I wish they'd done it earlier in the series (and perhaps they might have if DS9 had been made ten years later). They literally created a species where the actor could change unexpectedly but the character could live on in some form, and then, until Ezri at least, only used that conceit to look backward.
I don't think it's reasonable to compare six seasons of Jadzia to one season of Ezri. I like them both for different reasons, but, as I've said before, I think Ezri proved her worth when she finally told Worf what he needed to hear about the Klingon Empire...something that, again, I don't believe Jadzia ever would have said to him.
TL;DR
Ezri: Neat wrinkle in the series.
Better than Dax?: We don't have enough data to make a valid comparison.
Making the best of a bad situation?: The situation with Farrell was unfortunate, but in-universe this was finally tapping some story potential that had been there from the beginning and never utilized.
A mistake?: Perhaps more of an opportunity, given that it couldn't have occurred with any of the other characters.