Are you fucking serious? I pity you if you think Rom-coms have to be so bad. There are tons of them with mature characters too. In this one the author is playing with the gap moe (Strongest Knight v/s Behaving like a kid).
And this premise is getting old. He has basically run out of ideas and is dragging it with bullshit.
Don't teach me how rom-coms should be, I've read over 150 of them kiddo.