"This isn't about rejecting protocols that support IPv4"
Actually, it seems to be about just that:
The IAB expects that the IETF will stop requiring IPv4 compatibility in new or extended protocols. Future IETF protocol work will then optimize for and depend on IPv6.
That will only be viable when the IPv4 ceases to be used. The article refers to the the IPv4 address pool being "exhausted". This is an unfortunate choice of words. "The pool" is that of unallocated addresses and it's exhausted because the addresses have been allocated. The pool of IPv4 addresses being used is far from exhausted, it's pretty well full and there are a lot of them.
Replacing IPv4 with new IPv6 addresses won't be straightforward. A more sensible approach would be to assume that IPv4 will continue in use indefinitely with IPv6 being added and only change that approach when it becomes clear that in fact IPv4 use really has been discontinued in practice.