There are CDNs everywhere, true. It is not true that everyone deploys to them all, though. Also it dodges that the networks available to everyone are still not equal.

I think that "almost everyone" has a multi region cdn, but fewer have multi region application deployment, or cdn workers handling a significant portion of the application logic. My experience here may be incorrect or not generalizable, but I've rarely seen web apps that are slow due to latency loading static resources, but I've often seen slowness from high latency of the API calls and due to large static payloads.

That only helps the assets, does nothing when they run their actual backend servers in one of the US aws regions and your traffic has to traverse the planet anyway.