OK, first I’d say it must be really awful to be in such a situation, your partner doesn’t want you (or you your partner), esteem issues, etc. There are just so many of these threads recently.
AIBU to think this should be identified as a potential red flag earlier in a relationship? MN has some great posts on warning on people about being unkind, love bombing, going hot\cold, work ethic, how they describe ex’s, etc.
It’s such a critical part of the vast majority of good relationships, how can people not see the problem earlier? It’s one of those problems that just gets worse and worse if not addressed.