Surely the biggest cause of slowness is doing more stuff.

We don't turn faster hardware into faster programs, we turn it into more program. AI isn't going to change that. We'll just get even more program because the optimisation has freed up space for that.

Unfortunately most of the time, the more program isn't for our benefit. I note that by far the heaviest program I use is my web browser. The one thing I don't get to choose what code gets thrust upon me.