> That will do nothing for congestion within the core of the provider network. That's where qos is actually needed.
It isn't. Congestion in the core of the network shouldn't happen.
> Asking providers not to oversubscribe at all would literally increase the cost of broadband a minimum of 100x overnight.
That's conflating two different things. It's possible to oversubscribe and still have no congestion, because having 100% of customers all use 100% of their connections at the same time literally never happens.
As long as the uplink can carry the peak load in practice, there will not be any congestion. If it can't then the network is too oversubscribed, which should not happen.