If I had to ballpark estimate this, your iPad probably uses less energy per year than a strand of incandescent holiday lights does in a week. Maybe somebody can work out that math.
How do you suggest they make new iPads for people who want them? Someone has to make new CPUs and if you can improve perf/W while you're doing so you might as well.
Apple's started to roll out green energy charging to devices: https://support.apple.com/en-us/108068
If I had to ballpark estimate this, your iPad probably uses less energy per year than a strand of incandescent holiday lights does in a week. Maybe somebody can work out that math.