I am not trying to place blame, but I would word it differently.
Not to contradict you, but...
While the architecture has all along allowed for differentiating policy
restrictions, the app community chose to simplify their effort by
ignoring that there were policy differences in the lower layers.
Nobody ignored anything. To start with, the application community has had to work around these sorts of problems. This is why there are SIP proxy gateways, STUN services, and MX gateways. All of these exist due to connectivity limitations (either intentional or architectural). All of these cases fall under the "Got Lemons? make lemonade" approach. So I believe you've mischaracterised the community.
Eliot