Also the fact that the trans girl looks like a guy and seems totally dumb is super annoying.
Why? Does every trans character have to fit the "boy prettier than a girl" archetype? This is a reasonable scenario, she not being on hormone therapy and developing male characteristics due to puberty. Trans acceptance shouldn't be reserved to those who "pass".
also, no work of fiction is automatically less interesting for defending a cause. Sure, if it's designed to be didactic and only that, it can lead to something boring or downright condescending. But if you jump to that conclusion just because of the trans thematics, the problem is on you.
Not saying this manga is great literature (I can only put Kabi Nagata here) but it has something going for it.