While VPN's, the dark web and proxy technology exist, there will be a way to access pornography. You can stop the paid for services by threatening the payment processors to stop business with them (which is what is being proposed in the UK's Online Safety Bill as an amendment) but that won't work for the free and open source projects that can be forked and backed-up and for whom money is not the primary driver.

Ultimately I think the Internet will be deconstructed and split in two - an intranet like North Korea's Kwangmyong for the residential consumer and SME's with the Internet being heavily restricted to corporations and Government (ie. you can still browse Amazon US in Europe via Amazon's European country sites but not directly as you can now). That would make it easy to ban all pornography because the Intranet would be heavily regulated, licensed and unfree unlike the Internet today.

But then you will have a societial problem - what happens when the only outlet becomes via a partner and individuals are struggling to find a partner (think involuntary celibates). Unless you pick a fight, start a war and conscript them to die on the battlefield, they become a problem. Celibacy isn't the solution because we've known of dire consequences that have happened in the past when you have enforced celibacy on weak willed individuals. We also know from history that ultimately, banning vices does not work as what happened with prohibition in the USA.