A real sorry has no “but” stapled to it. Add one and it turns into a closing argument.

The word but reverses everything in front of it. Once it appears, an apology becomes the introduction to a defense, and the person listening stops hearing regret and starts hearing preparation. What they wanted was the acknowledgment on its own, with no conditions attached.

Say what you did, say that it was wrong, and then stop talking. Any context you need to add can wait for a separate conversation on a different day. If the silence afterwards feels uncomfortable, that discomfort is part of what makes it count.