To an extent. Maybe the system can still block location access, for example, but it can't force the app to gracefully degrade without it. A future version of WhatsApp could lock you out until you give it location, contacts, calendar, phone call log.

There are lots of soft-rules that Apple enforces around permissions that are still really beneficial. For example: the new "you have to be up-front about all usage of user data" would be nearly impossible to enforce at a technical level.

If all the apps that don't want to comply can just leave, you may find yourself relying on Apple services even more than you do now, because nobody else will respect their rules.