I wish to disallow building from certain groups in a whole world
But most of the protection plugins I find here only protect a certain area (so called ‘Regions’)
Could anyone bring a plugin like ModifyWorld back or suggest a plugin that disables building within the whole world?
You could use Foxguard to do this, by using a permissions handler tied to the _global region for that world. Just deny blockplace / blockbreak / whatever by denying the selected group the permissions with that handler.