Also, of course, with the removal of Baelfire, they messed up the larger plot of the show. The big story with Rumpel/Belle and Snow/Charming and Emma and Regina and Baelfire and Henry. That show is still unfinished as well. That is sort of the big writing problem of the show that will always be left unfinished. So in that way, the story for all the characters is left unfinished. The minor characters stories were much easier to finish.
I totally get wanting Zelena to have magic and do more with her. I just think as her character was now and the danger she was to the town and the family at large, that just getting rid of that danger helped that problem for me. It might not do a lot for Zelena as a character, but it helped the main characters and removes the question of what about Zelena without having to spend a lot of time on some sort of redemption for her or just flipping a switch on her redemption which they do a lot on this show.