First off, twists are generally handled very badly, being revealed early on. You don't really get mysteries to chew on, things to ponder, to try to figure out - it's all quite flat, things are explained not too long after even the shadow of a mystery about them is introduced (Imuru, Aria, Leviathan, etc.), and it makes the predictable, regular, and uninteresting pacing of events and plot hit even harder, extending to fights. It is generous to call them that, because there's really almost nothing to the fights which mostly work as powerlevel beatdowns with very mechanical 'lose for a bit then win for a bit then lose for a bit then win for good' type developments, such that it's hard to ignore due to the almost nonexistent power system.
As for the dialogue, it's generally just quite sloppy, sometimes repetitive, and strangely fond of using surface-level progressive 'references' that don't really mean anything much nor are all that coherent in practice, plus most characters act painfully stupid at the worst of times. Mammon funds racist organizations and says women should just be walking wombs (he's meant to be sorta likeable and has a very loyal subordinate girl though), there's a small lecture on why it is fat women are less common than fat men which is itself fine and relevant to the context, but doesn't really tie into anything at all past the moment itself, which is an absolute nothing-moment of no relevance to characters or plot or anything.
The characters are often somewhat flat or unlikeable. For highlights, Leah and Barbara are fun - Leah in particular is perhaps the best character - and of the enemy cast, Beelzebub and Asmodeus were the most entertaining, Beelzebub being just extremely evil with no compunctions but in a somewhat interesting way and Asmodeus being very much more twisted. In fact, a version of this story with Asmodeus as the female lead might've been truly fascinating - she IS the one who has the most personal stakes in making the Exorcist fall in love with her, unlike Imuru for whom it's mostly a job and somewhat of a 'hobby', as she wants to find anyone to fall in 'true love' with at all.
Speaking of Imuru, I found her to be generally very dislikable with few positive moments, a truly bland yet unpleasant female lead to follow and for whom it's hard to root for, and who has very very very little chemistry with the male lead. Genuinely, Asmodeus has a more interesting and depp understanding and relationship with him and she does it in about ten chapters of screentime, whereas Imuru is a pile of nothing but jealousies that could be replaced with a generic person to probably similar character development for the Exorcist.
Also, the manga likes to have a very 'all sides are kinda bad it's very gray' attitude. Some find it interesting. Some however could say that sacrificing captured people to a demon so he can devour every living person in East Asia because 'the church hates us', and happily chanting him on to go fuck 'em up, does not make the Witches very sympathetic. There's some sad backgrounds given around here and there to enemies - sometimes they're just kind of boring takes like rewriting the Nephilim to be misunderstood little guys, or having Satan and Lucifer BOTH be angels that are just around and Satan is the Wrath guy while Lucifer is the Pride guy, sometimes they're dumb like Leviathan's backstory (which REQUIRES her to be unfathomably, impossibly stupid forever) or the attempt to make Mammon and his subordinate sympathetic(? It's hard to tell that that's fully what the story was going for, but by all means it's framed that way with him saving her from killing herself even after he's banished and her talking about how she did horrible things and she really enjoyed it and it's all thanks to Mammon who doesn't discriminate on gender or race?!?). Beelzebub is the best foe because he has no sad backstory, he IS someone else's tragic backstory; Asmodeus is a nutcase and it's hard to say if she's meant to elicit sympathy - I suspect a little? - but that kind of ambiguity is fine by me, she's someone who took a tragedy, an obsession, and drew the most incomprehensible conclusion possible - which for a demon, I think was quite an interesting take in its specifics.
The Christianity theming was lame. The verses tend to be very superficially related to anything that's going on, it's all very surface level and tells you nothing you've not seen or heard before a thousand times if you engage with anything even remotely related.
Finally, I'd like to reiterate that the fights are pretty much nothing - there's no real power system to be spoken of, people just do things with occasional very vague indications of something more solid (man who poisons you with salt because he has salt powers because gomorrah, alchemy woman but it's kind of just to get the same generic miracle powers, demon lords generally do whatever the hell can be in any way justified in their sins, which aren't portrayed particularly interestingly or uniquely themselves), the protagonist is the Strongest but only when it's mooks or it's time to do the final thing (in this, I liked the Asmodeus arc most, as it veered away from that pattern), there's not much of any choreography or flow to the fights and it largely reads like an RPG in which each person does their thing then stands in the corner waiting for the rest to do it too, the tension also tends to be pretty lacking due to the predictable pattern and lack of shakeups for much of the story.
