I feel alot of people are forgetting something important, FMCs actions. Shes belittled, teased, interfered with his life and treated him at almost trash levels, why would he look at her romantically?
MC's loner path IS an unhealthy coping mechanism but she's going about this the totally wrong way. Like when MC was sad it wasnt a confession behind the school, it shows mentally hes subconsciously fine with breaking the status quo.
Also the whole group thing is stupid cause did they all forget MC turned himself into a stalkery villain in the classes eyes to save blondeys reputation and friendhoods. If he tried to join or forced to join her group it'd only fan those rumors again.
Ultimately the FMC is mostly serving her own purposes here cause she sees his life as poor even when he doesn't. Also theres the clear tsundere she wants to be with him although we haven't seen any reason outside he died to save her but treats him poorly and is suprised he doesn't see her that way.