What kind of ergonomic benefit would this bring to an average rust developer who doesn't go into the depth of rust traits/type systems and just use libraries made by other smart people to develop some web service backend?
So more flexible APIs and more efficient code for the consumer, and simpler library code (which is usually an improvement in reliability and maintainability).
https://github.com/rust-lang/rust/pull/96709#issuecomment-11... Has an extensive list of libraries wanting to use GATs, with their justifications.