I don't know, the Internet got on fine without those rules for a lot longer than we've had those rules, I feel like the gloom-and-doom over this is highly overstated.
Netflix and Youtube are probably safe from such actions now, but what about the much smaller services that try to compete with Youtube or Netflix, or podcast platforms, and so on?
Also this recently happened in Portugal, where technically there are some net neutrality rules now, but the current Commission canceled the previous Commission/Neelie Kroes' proposal to ban zero-rating. And since that meant they were allowed to do this sort of stuff, they went right ahead and did it:
https://pbs.twimg.com/media/DNGlrABUIAAr9RO.jpg:large
This is way more likely to happen in the U.S., where internet companies have local monopolies.
Actually no, all three incidents you mentioned (Netflix being slow on Comcast, Netflix being slow on Verizon, Youtube being slow on Comcast) were caused by peering issues. These are not net neutrality issues, contrary to Netflix's massive PR campaign to convince you otherwise.
The actual issue was Netflix opted not to peer with Comcast/Verizon, and instead funneled all their traffic through Cogent and Level 3.
The 2010 and 2015 Open Internet orders were a replacement for case-by-case enforcement.
Net Neutrality is a response to that overstepping. If the ISPs had just continued making ridiculous amounts of profit without upsetting the balance this never would have happened.