If existing regulations already solved the issues, then you wouldn't see existing ISPs giving unlimited data as long as you are using their special pet services or partner services.
But not to the explicit exclusion of other data streams, which was the primary concern of most proponents. And the mechanisms for implicitly excluded providers does already exist for them to challenge any such exclusion, were it to be proven.
That wasn't the only concern. If you only give free data for certain services because they are a) already very popular or b) have enough money to pay for it, then you create a huge moat for the incumbents and make it much more difficult for any new, better alternatives to compete.