My Roommate is a Gumiho is quite the predictable show. You can figure out the ending after a couple episodes and even the lessons it's trying to teach you are quite... shallow may not be the right word but it's so simple. While this isn't necessarily a bad thing it does mean that what will define the quality of the show is in it's execution above all else. Which was lacking, at times.

The first episode was great. Awesome setup for the rest of the story.

Then the second and to a lesser extent third episode came and the writers decided to add in terrible comedy. Like, I get that comedy/humour is subjective but this is that typical ''We're playing funny music and even though nothing funny has happened yet we want you to know it's funny and it's going to be funny''. More drama's do this. It's a cheap trick to lure you into a false sense of comedy, like setting the mood similar to the ''now sad music plays and we want you to know what's going on is sad'. It's like dividing parts of the episode into sections that scream some forced inclusion of comedy rather than letting the viewers themselves decide whether something is funny or sad. Except that seriously just went on for half the episodes if not longer. The female lead making over the top faces or eating disgustingly on purpose. I'm sorry it just doesn't work whatsoever. Luckily the show tones down on this a lot after the first couple of episodes because holy hell I was on the verge of quitting the show right there.

With that out of the way the rest of the show was a mixed bag but it did have more positive moments than negative moments as the show went on.
BY FAR the biggest strength of this show is in the two leads. But for me that's also where part of the weakness was.
Allow me to elaborate on the strengths.

The lead's relationship progressed quite nicely. Yeah some predictable breakup/misunderstandings we've all seen a hundred times before happened but I think what truly made it greater than the show itself is the way the female lead was written.
Most of the reviews mention the realism of the female lead and I would have to agree.
Have you ever watched a relationship in a kdrama and got really annoyed that the characters weren't talking?
Yeah, that doesn't really happen in this one. Conflicts are resolved incredibly quickly in a natural way; ''hey, this is going on and I want to know why/what's going on''.
Very refreshing. This is by far the greatest strength of the show. The female lead was in character untill the very end and because of this the show was a lot more enjoyable to watch.

I didn't however really feel the chemistry between the two leads, I felt it a lot more with the second leads.
Chemistry, however, is subjective. I think many people will be able to feel it and therefore enjoy their relationship a lot more. While I think the feeling of love was acted well by both leads I didn't feel a spark. It felt like they were desperately trying to create that chemistry and the acting certainly wasn't at fault it just... I just didn't feel it, you know? Ultimately just a subjective observation that will be different for other people.

Regarding the story it was quite bare bones. Though it didn't have to be very detailed to begin with. The whole gumiho plot wasn't really explored at all. It just existed because that's what the show was about. Perhaps It's just my lack of knowledge of gumiho's and for koreans it will all make sense but I would've liked a bit more exposition and world building.

Lastly, there's an age gap. The male lead is about a thousand years old but his character is in his thirties while the female lead is early to mid twenties? Do with that information as you will. Age gaps quite literally never bother me if it's between two consenting adults because I've got better things to do than spend my time judging why people should or shouldn't love based on some arbitrary reasoning. The reason I bring it up is simply because many people do care. So be warned/informed.

Some smaller things about the show;

Soundtrack was non existant. Nothing memorable to the point where I can't even remember a single melody despite finishing the show only 10 minutes ago.

Production quality was up to standards. Mind you I've got 0 experience about directing or cinematography but if nothing stands out as poor to me then I will consider it a job well done.

TLDR: Average show. Strengths are in it's characters and relationships while it's flaws lie in the very mixed comedy, non existant world building and barebones predictable plot .