I didn't know the #Vocaloid5 Editor was that controversial. I liked it a lot and the Premium Edition's pricing was reasonable if you had purchased #VOCALOID V3 or V4 Editor especially since it included CyVa and SongMan.
I think the tech upgrades from V4->V5 are even more than V3->V4. It brought back some of the fine editing and tuning we haven't seen since V1 days. Also, they added VST mode so great for integrating into your DAW.
#Yamaha has a lot of failures to answer for in Vocaloid 5, mainly in marketing, 3rd party support, lack of diversity in voicebanks, and their basic abandoning of the platform to chase "AI" tech, but I don't think the Vocaloid 5 Editor, CyVa, or Songman were part of the problem.
Really outside of price, which is a personal problem and not something I am willing to argue, I don't know where a lot of the anti-Vocaloid 5 sentiment comes from.