My issues with the Demetria route could be summarized in 3 things:
This first one is kind of shared in all the new routes (Rye's, Demetria, and Claudia), but it is more egregious in Demetria's route, my issue is that the route is never really given an explicit reason to be. What I mean is that we never really get a reason why MC is pursuing the futa they are pursuing, in the original 2 routes we get a clear and explicit reason for both of them (Suni is the nicest person MC ever met probably, Vicky saved him from certain rape). Rye's route makes a bit of sense if the MC had the talk with Rye in Vicky's route but otherwise feels a bit random, Claudia's route can be excused due to the shared history between Claudia and the MC, but Demetria is just like "yeah imma go to the church that preaches male submission, do free manual labor, and then chase the dickpope; I can't see a scenario where this isn't beneficial to my person". I think they could have written some interesting reasons, and I'm not saying every route needs a super logical reason to be, but the ones that don't should at least show the MC is aware he is doing something a bit absurd and questioning himself a bit, even if in the end the only reason he can find is that he has a kink for whatever futa he is pursuing.
The second issue is that whoever wrote the Demetria route seems to have a bone to pick with religion, I don't mind that in itself and it made for some good satire during the route, but there isn't a single time where the route addresses anything spiritual or any kind of religious awe. We don't get anything regarding why Demetria became a priestess despite her bisexuality being shunned, we never really see much of the MC getting spiritual about any of it (which makes his trials even more pointless? Mostly he is just making a point he is good enough to endure them, and then in the end he kinda randomly falls in love with Demetria and uses that to push himself further), so for it being THE religion route, it felt pretty underwhelming. Maybe this could be adressed in Mallory's route, but she seems more evil than Demetria (tbf half the cast is entirely evil outside of their routes so who knows), and I suspect that in Mallory's route they will satirize the "mindwashing" aspect of religion so not much hope on that route having a good spiritual story. Also the ending straight up sucks, again, MC kinda randomly falls in love with Demetria, becomes her chosen male, and then gets whored out on random events because Demetria and the church needed more clout. And that's supposed to be the good ending. What a bummer. (maybe it gets adressed if the real good ending is convincing Demetria to come forward about her relationship with Claudia and MC gets in a nice threeway relationship with them, but only the future will tell)
The final and third one, it just isn't really that hot. And I'm not talking about the setting or the kinks, to each their own. What I'm talking about is that it feels the artists got kinda lazy with some visual aspects of it, we never get a good full frontal nude view of Demetria's assets, pretty early in the route it is kind of ridiculous how in the text the MC is saying something among the lines of "and she is gorgeous, her cerimonial clothes leave little to the imagination and you can see she's really large" and the portrait doesn't reflect any of it, there is no visible bulge or anything like that. Rye's mom also had this issue by being the only one that didn't have a visible bulge in her swimsuit (despite canonically being larger than Rye and Renata). Just lame we don't get a good look at Demetria in her own route.