there are a lot of work-in-progress features that are important so we can write ...

there are a lot of work-in-progress features that are important so we can write more maintainable code, like GAT.

but it's also true that there are quite a few threads that are conceptually simpler than GAT and are just left unfinished.

and there is a very serious push (or pushback with regards to GAT) to keep those promises.