Or ... just maintaining two frontends is a lot of work? For something used by relatively few people? No conspiracy needed.
And I believe gmail works fine with Firefox? Did last time I used it anyway. Does it not work for you?
And gmail still supports POP/IMAP and SMTP I assume? Whenever I had to use gmail for work I used to Hillary my emails to FastMail. Always worked pretty well. Can also mutt or Thunderbird or whatnot.