I had a teacher who refused to let any of us say “its okay” because of this exact reason.
It has taken me years to learn that it’s also okay to say “Thank you.” when someone apologizes.
It is perfectly acceptable to acknowledge that someone has apologized, and still refuse to accept their apology. There are things in this world that cannot be apologized for.
I feel like you can tell a lot about a person by how they react when their apology is not accepted.
For example, if they get mad and accuse you of being a bad person for not accepting an apology, they never meant the apology and were probably gonna do whatever it was again in the future.