Except that they wanted to use Dax as a full time character. And the Trill species left them a wide open door to both let the actress leave and keep Dax, if not Jadzia.
I don't agree with this one at all. As much as I loved Jadzia, I think keeping Dax in the mix with the new host was absolutely the right call. It took them a bit to find the right voice for Ezri, but she created drama amidst the characters, expanded the lore, and gave us Nicole deBoer. I may be biased, because the pre-Picard EU made Ezri into an excellent and well rounded character.