I'm not complaining about having different kinds of opposed checks. I like that there are lots of different things to target, in fact I wish different kinds of checks were more accessible so that combat was more varied.
I just find it weird that they have different game mechanics. Like, attacking has the player rolling against a defender's static DC. Except actually sometimes the defender rolls to save against an attacker's static DC? And Dex saves are actually represented twice, once as an actual save to dodge things, and once as AC. Precisely because there are those two overlapping systems at play.