Wow, this sounds like a debate worth having!
Personally I’d love to see hanging again. It’s easy to set up and people can witness it easily. Would be good to have it more public - maybe more deterrent and also maybe people would start “picking sides” booing the victim and such (much like stocks did).
But if people are worried about “humanity”, why not the gas chamber? Can’t get better than that, knocked out just by breathing like laughing gas. Better than the needle.
Actually hanging is highly technical.
The US Army had a very exhaustive manual on the subject detailing the length of the drop depending on the height and weight of the subject. The placement of the noose and not.
If you got it wrong you could decapitate or slowly strangle the victim.