What, then, does their eagerness for prioritization tell us? It tells us that these companies would like to stop investing so much in increasing capacity, and instead squeeze as much money as they can out of their existing infrastructure.
They're going to make things worse (or let them gradually become worse over time) just so they can charge extra money to people who need something better.
Beyond that, prioritization is not in conflict with net neutrality. If my ISP wants to offer me a premium subscription that prioritizes my traffic over normal subscribers, that's fine. Where we run into trouble is when they start doing this for other people who aren't their customers. If they want to charge me more for better service, that's fine. If they want to charge Netflix more to provide me with better service, that's not fine.