The QoS features built into hardware are usually intended to be implemented when the network is congested. The ones that net neutrality advocates are arguing against are not. Even net neutrality adherents accept contracts that, for example, allow users to be deprioritized when the network is busy based on their total usage, and they complain instead about ISPs trying to be selective about which traffic they will affect. I have already explained what the ISPs have done and would like to continue and expand which lead them to this opinion. I have a few other points about your last comment though.
"the 'user' generally has no service with the ISP, which is the problem. They create congestion, but don't pay the ISP to deliver any of the traffic served."
At first, I thought you were talking about the customer of the ISP. From your next sentences, this appears not to be true, but in case you were including both of them, the customer is certainly paying plenty to the ISP for all their stuff. But, as I say, this sentence suggests you were talking about the other end:
"They don't contribute anything towards the cost of capacity upgrades needed to deliver 4K adverts, even when they make lots of money pushing them to the ISP's customers, who generally don't want them."
Which is how the internet has generally worked. The ISP concerned is sending that data on because their customer has payed them to do so, and they received it from the ISP from the service provider, which has likewise been payed to do so. Those two ISPs may negotiate an agreement where they exchange data for free or where one of them gets money as a result, but either way, they will figure out a way to deliver the data from one paying customer to another one. That the data sent makes money for someone is irrelevant; they have already agreed to provide the service by signing a contract with the customer, and it is their responsibility to do so no matter who is making money using the service or how successful they are. Similarly, if I use an ISP-provided connection for something which makes me no money, I don't get to either have my connection for free or send the bill to every site I used, because I looked for a company that agreed to exchange bits and payed one to do so. Your electricity provider will not charge you more if you're using it to charge your work computer, and thus, get money. Your water provider will not charge you more if you're using that water in baking something that you sell, thus turning a profit. Your ISP doesn't get to do it either.