In their defense, it's not like they're hallucinating - the author is definitely using unaswered questions to create a sense of uncertainty and unease in the protagonist and, by extension, the reader. I can almost see how somebody who feels "once-bitten" by a Rent-a-Girlfriend or something might see a questionably-available love interest and Threatening Male Presence as "cuck"-coded. The imagined husband in the dream was obviously intended to be threatening to Otakei, because he's not presented as NTR Man as might typically befit a gal, but a successful adult man in a suit - jabbing right at Otakei's deepest insecurities at the moment. While it's obviously not literally cuck shit/NTR, playing with the idea that "you might never be enough for her" is a distillation of a certain kind of fear central to that experience, I think.
I do disagree with their assessment, because we see that the dream was part of (or motivation towards) coming to terms with the fact that he just might love her, rather than just a treat for the masochists.
But if this reader is like "this makes me uncomfortable," then yeah, I think it's trying to do that... but only a little. If it makes you very uncomfortable and that's not what you come to romance manga for, then UdenEmpati's right and maybe one of the other, teen-focused Otaku x Gal stories is more appropriate.
It's interesting how the people who are really triggered by this seem to be ones that are focused on the romance and have very specific expectations about the story playing out in a typical fashion. Personally, I'm more interested in the rest of each character's story, like what kind of evidently heavy shit happened with her husband, and how dude's manga's gonna do. With how the series has approached things more maturely and showed that the important part of their artist-and-muse/cheerleader relationship doesn't rely on romance to work, I'd already still be satisfied by an ending where they don't wind up together but were simply important parts of each others' lives for a while.
I'm kinda surprised the other complainers are still sticking with it six chapters in, honestly. This seems like it would be a really boring hate-read.