Something to point out is a lot of this post is discussing enterovirus's, not the polio virus (a specific species of the genus Enterovirus, specifically its species is Enterovirus C). The eradication of polio is in reference to the eradication of E. Enterovirus C, not the eradication of all enteroviruses.
Edit**
Stating that just because they are similar that they are the same is like saying that chickens and turkeys are the same, and if a country were to eradicate all of the turkeys that they could still hunt wild trkey because chickens. Your example isn't quite as extreme because different enterovirus species are closer in relation than turkeys and chickens (as the relation between turkeys and chickens ends at their order) however the context is the same.
No, it's not quite the same. I'm actually questioning whether the polio virus has indeed been eradicated if we are seeing other enterovirus cause the same problems, i.e. paralyzation and death.
Again, there are different strains of flu virus. It is true that each one is distinct and not all will cause the Great Flu epidemic of the 1900s. But flu is still a big deal.
Considering that we have enterovirus still behaving like poliovirus and having the same complication of paralyzation, I don't think it's unreasonable to say we still have a form of the thing we feared running around loose.
I also forget to point out that CDC article I linked to discussing enterovirus with complication was an Enterovirus C strain - C105. So enterovirus C is not eradicated at all and is almost indistinguishable from the strain traditionally associated with poliomyelitis.