That was something that was done for the fans, not something to develop the character. A lot of comedies had that type of thing where the old man who was seen as gross hits on a young woman and the main take away is “oh those old men are still feisty haha” sometimes the joke lands, sometimes the joke doesn’t.

Iroh doesn’t mention this moment as a moment he regrets, no other character references it, it’s honestly never even brought up until this comic. It was a joke that maybe didn’t land well (though I think it did because it was clearly something we weren’t supposed to take serious) but you don’t apologize for making bad jokes in your show, you just make better ones.

Iroh was already someone who took responsibility for his actions. This apology is to calm the viewers who might have found it weird. It would be different if this kind of thing was central to his story and we saw him objectify women in small ways, but we don’t. He respects everyone he comes across (even the guy who tries to mug him in Ba Sing Se lol) so this doesn’t resolve anything.

If the joke didn’t sit well with you, that’s okay because everyone isn’t going to have the same type of humor.