I am all for apologizing about past behavior that has hurt/disrespected people. But when it's accompanied with a hefty dose of "I'm sorry you're so lame," it come across as an attack. Same with the "I'm sorry I'm the worst person ever to walk to earth" bullshit. Maybe this is just the fact that I was raised by a narcisstic alcoholic asshole, but apologies made in that manner can be actual attacks or slams. I've seen it quite a bit in gaming, RL, you name it. It's why I think if you want to come across as genuine apology (vs confessions of being a dick once upon a time, hey, I think we've all been there), just saying "I'm sorry" does not invalidate dickishness afterwards.
Public apologies that are non specific (vs confessions) also run the risk of anger by other folks who feel similarly wronged by that person feeling like they're getting a second slap when that's not acknowledged. (I see that more often online than RL), mostly because other people who have been subjected to the behavior physically standing in the room are not as easily overlooked either accidentally or on purpose.
Apologies are by their nature risky. You are extending vulnerability by acknowledging your role in harming (shallow to deep) someone else. There is no guarantee of acceptance. It's not a face saving measure. Sometimes it opens up old wounds. I think sometimes folks are not always aware of that. But I do think that's why a "but" or "if" apology makes many people so angry again.
Anyway, just my thoughts as someone who's had to apologize many many times online and RL to a wide variety of people,with results ranging from being told in no uncertain terms id never be welcome in that person's life again, to a repair and strengthening of a vital relationship and most often of the dull "thanks I appreciate that" inbetween.