Well a lot of the improvements cost more computation. I wouldn't be surprised if low-computation video had only improved slightly, but it seems like it has improved a lot. The advantage of h264 is hardware adoption much more than actually being computationally cheap, it seems? Well, maybe. The thing is, I don't know how the decoders scale. Can you make a decoder for a constrained AV1/h.265 in the same hardware space or maximum CPU budget as an h.264 decoder and still see very big advantages?