Why does "my SO would rather do something else than spend time with me" mean "my SO's life doesn't completely revolve around me?"

It's possible that OP overreacted to something that shouldn't have been an issue. It's also possible that OP's ex was ignoring him/her (and for the life of me, I still can't figure out why some of you think that that is okay). It is, however, highly unlikely that the situation was anywhere near as extreme as you seem to have decided it was. You really kind of seem like you're projecting onto a secret that is quite vague and inconclusive.