This is a breaking change for us, as we rely upon loading assets from the Resources folder through addressable via GUID. We tried migrating to bundles, but our pipeline is not designed for it. Our only feasible solution is to fork the addressable package and re-add this deleted functionality.
Is there any comment from Unity on why this was deleted?
CreateBuiltInShadersBundle was deprecated in favor of CreateBuiltInBundle and the name _unitybuiltinshaders.bundle was changed to _unitybuiltinassets.bundle. Everything seems to work with that minor fix.