I-frame placement isn't hard; it's very obvious when a scene changes or when an I-frame would be profitable. You generally need to have them far more often than you'd like anyway, as otherwise you can't seek in videos.

The main advantage of ML for video compression is that people accept giant ML models, so you can hide a lot of common "features" in there. The disadvantage is that classical codecs are macroblock-based for a reason; you can't just process a whole frame at a time, nobody has the memory bandwidth for that.