I imagine it'd be a jurisdiction issue for what you propose. If, say, the UK mandates that websites block VPN nodes, that will affect websites served from the UK (creating a Great Firewall of Britain). But what about websites served outside the UK? Those websites can't possibly tell if a user is from the UK and using a VPN, vs outside the UK and using a VPN, so they can't only block UK visitors—they'd have to block all VPN traffic, which is probably not worth it from a business point of view. I suppose the UK could then deem that website illegal in the UK and block them, but then that'd only block the website for non-VPN users in the UK... But if the website owner is outside the UK they can't be punished for violating that law.

More probable (though I still think unlikely) is that a country could sniff for e.g. Wireguard packets and block those. But again that's unlikely because of businesses using VPNs to let employees access company intranets at home.