The amount of data you need to provide for ESTA and a B1/B2 US Visa is not remotely comparable - the visa process has way more steps and requirements.
That's about to change, they are about to introduce a change that will require bios of all relatives, all social media accounts, email addresses, etc. Haven't looked at a US visa recently but it seems as invasive.
Depends on the visa.
A-1 and A-2 for example require almost nothing beyond a photograph, and a letter saying you’re travelling on behalf of your government.
So it's a "lightweight" visa.
The information you need to provide as an Iranian after a P1 visa is not remotely comparable to a British citizen after a B1 visa either.
"you" being the operative word. The rest of the information will just be supplied by your government instead of yourself.
But then some countries have visas on arrival that are less of a hassle than ESTA.