Things have not regressed. Have you driven in a modern car? Flown in a modern plane?

"Why shouldn't a motivated/intelligent layman try and get hold of those devices and learn them?"

Why don you buy a typewriter and write Shakespeare?

You really just assume that you, untrained and unexperienced would be better than a trained professional? You would really cut open your partner or child, cut out a section of their bowels, sew them back together, and know all the right drugs to give and have the half million dollar anesthesia machine? Do you have the MRI machine you need to diagnose this?

It's the same reason we don't just let anyone work on airliners.

Someone who thinks they can do this is dangerous, and borderline psychopath. I'd encourage them to watch one live surgury first. Saying you can fo something like this without even seeing it once is why this shows too much unfounded confidence. Yikes.