With NN in place, there’s nothing at the network level that prevents a competitor to them from rising up. Without NN, ISPs can make deals to speed/slow/block traffic to different destinations, which would have a real effect on possible newcomers that challenge the incumbents.
I've come to this conclusion because NN is effectively dead at the link level, not the ISP level. Try posting a link to the web on any of the big social sites, and you'll be instantly downranked.
Not saying your issue also isn’t valid, but it can be addressed by market forces when enough people get sick of that type of behavior (like Twitter/X) and move to something else (like Bluesky). Most people don’t have any real choice between ISPs (through monopolies that have been granted to them for decades by local governments), and therefore there needs to be some additional legal protection against that type of behavior.
Trying to lump them both together under NN is part of the playbook that Big ISP has been using for years to muddy the issue.