And what's the hold up on that?
I'd guess it would take porting the game over to a different branch of Cobra, which would probably involve a lot of asset modifications and a lot more testing. If they wanted good results with AA, they'd still need to do something about the degree of specular highlights that are almost everywhere in on-foot content as well.
I've been playing with the newest versions of ReShade, plus some shaders that can generate motion vectors then apply TAA and they work, to a degree. The motion vector quality is no where near as good, or as cheap, as it would be if the engine had good native support, and the combination of AA needed to meaningfully reduce the worst aliasing offenders is quite blurry, even with an aggressive sharpening pass. Some significant aliasing is still present as well.
This taste of what can be done leads me to believe that, even if it were relatively easy to do a straight port (though I don't think it is, given how hard it was to move everything to the Odyssey build of Cobra in the first place), or somehow bolt-on motion vector support, they would not want to do so just for the motion vector information that would make TAA and all it's derivatives (FSR2/3, DLSS/DLAA, XeSS, etc) trivial to add. Without a lot more work, it would seem like a half-measure, with results that would disappoint a lot of people. I suspect this is what's holding up the general AA front as well...nothing easy to integrate does enough, and doing enough to make it worthwhile means doing more than they can afford to devote to the problem. It's not like Odyssey doesn't have other issues.