Criminally Underrated BL

Why the low rating?
Boring, slow-paced, 4+ year miscommunication

Why it's worth your time:
Unrequited love is inextricably linked to ambiguous feelings about the MC's home town rather than just being about one person; explores the fears of stagnation and being left behind; understated and subtle story that is premised on more than just bog-standard "miscommunication"

Why the low rating: insufficiently dramatic, no jealousy from the older brother, rushed, unresolved

Why its worth your time: lack of definite romantic resolution is fine since the point of the story is the POV character's emotional growth through his lingering feelings for someone and not the romance itself; does a great job of showing a family/friendship dynamics when one older sibling is academically gifted; excellent attention to complex & nuanced feelings; story about growing up emotionally

Why the low rating: All the mangaka's works tend to get lower ratings than they deserve - a combination of substandard art and different subject matter. In this case, the ending is said to be unsatisfactory.
Why it's worth your time: ending is perfect for the story as it is set up; a nuanced exploration of two characters coping with their respective father figures; intelligent writing; great pacing; one of the author's best; relatively happy ending; story that doesn't insult your intelligence.

Why the low rating? Confusing, atypical art style, slow

Why it's worth your time: not for those wanting basic pretty-boy BL (the art is quite good, but the distinctive style is polarizing); a series of well-written interconnected stories that remain politically & ethically agnostic, featuring morally compromised/complex characters; truly mature, understated BL that refrains from moralizing (if you like this, there are numerous sequels that are equally good)

Why the low rating?
Love triangle where the bulk of the story is dedicated to non end-game relationship; passive main character; didn't like end pairing

Why it's worth your time:
Mature story, complex characters, good development; takes its time with things that are peripheral to the romance but important for understanding the characters; every character is treated sympathetically; excellent if you don't have an allergy to complexity and ambiguity.

Why the low rating? Sad, "weird," unlikable characters

Why it's worth your time: excellently writing aimed at an older audience; nuanced treatment of complicated, morally ambiguous, realistic characters; has a nice mix of sad/hopeful/bittersweet endings. A true hidden gem (at time of review, it only has 57 ratings).

Why the low rating? Unclear from the comments, but I'm guessing its because readers went into it expecting the main character to be gay (it's the POV character's father who is gay and in a relationship)

Why it's worth your time:
A delightful portrait of unconventional family dynamics; well-paced and well-written comedy with atypical characters and a lot of laughs; not BL, strictly speaking (the story is about more than just the relationship), but most BL fans would probably enjoy it

Why the low rating: Very few comments so no consensus. "Boring"? "Tragic"?

Why its worth your time: A varied collection on the theme of boxes, ranging from melancholic historical stories to goofy, high-concept school life romps. Not every one is a masterpiece, but the mangaka is one of the more interesting BL writers so each short has something distinctive and interesting. Far from being boring, the smorgasbord of box tales is worth checking out and deserves more love.

Why the low rating: "weird, twisted, tragic, boring."

Why it's worth your time: Only "weird" in the sense that the author doesn't conform to worn BL modes and styles. Some stories are tragedies, but most are not. Stunning art, creative and varied modern riffs on classic tales. Like folk and fairy tales, the stories don't go into a lot of detail or depth, but remain nevertheless evocative and satisfying. If you want something a little different, this is excellent.

Why the low rating? Lack of resolution, feels "empty."

Why it's worth your time: Refreshingly nuanced; leads are more like real people than the idealized types you see in most BL. Not a story to pick up if you want something with an easily digestible lesson or pure romance. While not every single thing is neatly resolved in the usual BL way, the arc is suited to the themes and struggles of the characters and perfectly satisfying.