Quite often, “get over it” is said to people who are on the receiving end of prejudice and oppression that they are still experiencing. So how can they get over it if it is still happening? Make it stop, then there might be some legitimacy in saying “get over it” — except that they will still be living with the legacy of it.
I also really dislike it when people who are grieving are told to “get over it”. Not gonna happen. I once read a helpful thing that said that grief doesn’t shrink over time — our psyches expand around it. (Helpful partly because often grieving people feel guilt once the grief seems to recede.)
Maybe we never get over things, but that doesn’t mean we always live under them. It means we assimilate, over time, and we start to live and breathe again, and although it’s never quite in the same way, the difference doesn’t mean our lives are worth any less.