The complaint isn't that iPad is useless, but that it would be equally useful to nearly every happy iPad user if it had a few generations older CPU.

iPad works for lots of people, but the things that iPad is best for don't really need a powerful CPU.

There are few "Pro" apps that you can run to prove it's possible to run them (except for plugins, OS-level helper apps, extra hardware, background processing that doesn't randomly die, scripting more fine-grained than shortcuts, competent file browser, etc.) but you can max out the CPU for a few minutes and go back to a macbook for real work.