Classless interdomain routing is not the point of this post, but basically we started giving people more options for network sizes, and while complex in implementation, it was philosophically virtually uncontroversial.

You’re talking about 2 different things here. Bit masking part of what is now CIDR was implementable since the mid 90s on network segments, it’s the logic to route packets based on CIDR that was integrated into RIP, GRIP, and BGP.

Also, CIDR can’t alleviate multi-hop routing address exhaustion.