Instead of forcibly updating sites, could they be forcibly expired?

People have their reasons for not upgrading (assuming they’re still in control of those sites, or not dead) in the same way people have their reasons for not wanting to use the block editor.

So if we’re going to forcibly update them, why not do it to a cut-down, restricted version of WordPress (say, based on 4.7), with no access to plugins or themes, cut-down Dashboard, no hijackable backend functionality… WordPress, in name only, but with an upgrade option should site owners wish to opt back in to a more modern WordPress experience.

Not the easy option, I know…