Email is an open protocol. Anyone can write a client. All major ones work with Gmail. For YouTube, see newpipe. The main missing piece is Google maps (at least the navigation bit) which you can't legally get without explicit cooperation from Google.
EDIT: A quick search shows it was always disabled by default, since 2007, when it launched.
That's not the case for YouTube, though, which is exactly why it's a problem when GMail isn't.