The reason why I think Jill's & Sage's confessions of love are the best (alongside Maya's) is because they come from a place of affection and actual love.
Josy doesn't quite 'love' MC, she loves the idea of being with MC. Out of all of the love interests, she's the only one who lacks a deeper connection with Tremolo. The reason why MC & Maya have a stronger bond is because of not only her problems with her dad, but also due to their personalities. She's a bit more shy and he's a bit more assertive. Opposites attract in this case. She's the opposite of Josy: she wasn't really interested in MC at the start, at least nothing more than a friend. But she grew to like MC 'that way' due to his caring nature and her vulnerable emotional state.
Josy's obsession with MC is no different than Zoey's desire to be a surfer: she tries it out and it's rocky. Just like Zoey eventually gave up on it because it wasn't just how she dreamed of it, Josy & MC's relationship is doomed to fail due to a one-sided infatuation from Josy's side. MC doesn't feel that strongly for her, even on a Josy-centric path.
That's just my reading of it ofc.