Silicon valley has now given a $250M valuation to an email client with keyboard shortcuts.
And it is so much fast because... wait for it... it caches things locally and isn't delivered as a webpage.
I also want to say if you want most of these features you can just get Mailspring, it is great and Open Source.
Even available as a Snap maintained by the developers
A server setup for the users of gould.cx to connect to the greater ActivityPub network.