The old marketing page for the Delta Shuttle was pulled down some time in late 2021. This is one of the last snapshots before it was pulled. The page now does a redirect to check-in times page for the Shuttle, but it's not really clear it's still a thing. The mainline flights on these routes say nothing about being part of "DL Shuttle".
https://web.archive.org/web/20211016...a-shuttle.html