I'm amazed at how many folks on this forum see the Web UI as intrinsically tied to the service. As someone else rightly said, e-mail = IMAP + SMTP. That is true of Gmail as well.

Frankly, I've always hated the Gmail web UI, so I never use it. Not in the 22 years I've had a Gmail account.

IMHO, Superhuman gets a ton right... A Superhuman clone (maybe in VIM or Emacs) would be ideal if you don't want the AI features or the $40/month fee. Don't even need to change your mail address, since it connects to Gmail.