What a waste.
Something went wrong, and the other person cared enough about the relationship to let you know.
Perhaps they’re hoping that you can rebuild a bridge. That you can see what they see and care enough to do something about it.
A half apology is a little like half a balloon. It takes effort, but it doesn’t have much utility.
Honoring the moment, an apology is a chance to reconnect and actually move forward. If that’s not your goal, a half-apology might be fine, but don’t expect much to come of it. If you can’t see or accept the other person’s situation, you haven’t responded to the very thing that prompted the apology in the first place.
The opportunity for an apology is just that–an opportunity to demonstrate to the person you care about that you see them, understand them, and are concerned enough to extend yourself.
The useful apology celebrates the relationship and takes responsibility for what went wrong. It’s hard to minimize your way through this moment. Empathy and care might be a more useful alternative than trying to get it over with without too much responsibility taken.