Perhaps the definition of net neutrality could be extended to cover this problem. I mean, if we want an internet where everybody is treated equally, then symmetric upload/download speeds are a basic requirement.

The tricky thing is that ISPs have traditionally offered symmetrical service, but only as "business class". So they would protest that they already sell that, customers just need to pay (double, triple) to get it. That said, my (just residential) fiber connection consistently tests slightly faster upstream than down.