long-time java dev and did a portion of my startup on dial-up. they've been hostile to any attempt to optimize for bandwidth for a very long time - i had elaborate hoops i jumped through to implement caching that should have been baked in to the tooling

this is just chickens coming home to roost

The interests of the Maven project (i.e. the Maven community), Sonatype and other actors in the space are not necessarily aligned.

But I do wonder where you had to jump through hoops? A basic Squid caching proxy should be enough at least for a pure pull-through like Maven Central. Once you have to publish stuff, okay, that is messy, you won't get anywhere with just Squid there.