This is reminded me of a 1940's screwball comedy, and really you have to forget it's supposed to be a high school rom com.

Some of the comedy scene's, the one in the lift rivals Rachael and Samantha, are memorable. The rewatch value is mainly for those scenes.
Yes you have 20-30 somethings playing teenagers, and the sad backstory, The leads are all good actors, so its polished.
I never believe in love triangles, so the fact there was one is just a plot device and you have to go with it.
Who ever did the set dressing for the book shop and the family home deserves an award, I could smell the rooms, they looked lived in, so they were not acting in something that looked like a set.
Just submit to the genre and have some fun.