You seem to be arguing that marriage is a dumb legal thing, ergo relationships are not important. Even if the premise is true, your conclusion is unrelated.

With empathy to the OP, this sentence > Plus if someone is bailing on you when you’re finishing a degree they definitely weren’t going to be there for you in actually troubling times - like an illness or your house burning down

Is also kind of fucked up. There's no particular reason to suggest their partner left because they were unwilling to support a partner through a tough time. Maybe it is the case. But that's a very aggressive assumption that implicitly strips the lost partner of any individual autonomy.