I think if I felt at all convinced by or invested in Aang and Katara as a romantic pairing, I would feel gypped by that, on-screen mutual smooching or no.

Come to think of it, it's a shame none of their actual conversation time was spent on the non-romantic bits of their relationship--the faith, the support, the teaching, the inspiration. I suppose this does not bother me much because a lot of that forms the undercurrent of the crush, and therefore is covered indirectly, and friendships and mentorships don't necessarily need a dramatic finale when you have every reason to believe the participants are going to remain major parts of each other's lives in the future. Zuko and Iroh really needed that onscreen conversation (and that Zuko-Toph conversation back in Ember Island Players) to be satisfying, specially as Iroh's just now patting Zuko on the shoulder and saying, "Go on, now, I'm done teaching you." But the teaching thing and the friendship thing with Aang and Katara has already received its due, so the lack of addressing it here--in favor of making their screentime all about romance--doesn't feel like a gaping absence to me even as a viewer who doesn't care much about the romance.