IIRC gmail doesn't support any capabilities from after ~2003.
In order to synchronise with this kind of server, you need to list UIDs and Flags from all mailboxes and perform a full comparison of which items changed. There's no NOTIFY, so you need to do this periodically.
This requires substantially more network and processing, and an entirely different application design. Such a design cannot immediately synchronise new entries either.
ImapGoose doesn't cover this kind of scenario, there are plenty of existing tools that can synchronise legacy servers already.