It's possible that all of these things made Tartarus lose interest, and MoM just might be the straw that broke the camel's back. I guess since KH3 was the end of the Dark Seeker saga, most people find it easy to hop off here.
It's clear that the series isn't what it used to be, but I also never felt like KH1 -> CoM -> KH2 was its peak, either. In my opinion, UX has the best writing to date, and this is post-KH3 material. ReMind's scenario was a retread, but it had a lot of elements that fans loved, and in a lot of ways felt like a love letter to KH2. Dark Road so far might be in the beginning stages, but the lore we're getting, as well as how Xehanort and Eraqus interact with their classmates is fascinating. People give DDD a lot of shit, but as time goes on, it's clear that DDD is going to be a game that makes way more sense as the story unfolds. And KH3 is my favorite title to date, other people hate it, so to each their own.
No matter how you slice it though, some things just aren't for everybody, and it's better they come to grips with it now instead of torturing themselves with something they don't even like anymore. I don't agree with the series going downhill, BUT I understand and respect their opinion.