Firefox on Debian stable is so old that websites yell at you to upgrade to a newer browser. And last time I tried installing Debian testing (or was it debian unstable?), the installer shat itself trying to make the bootloader. After I got it to boot, apt refused to work because of a missing symlink to busybox. Why on earth do they even need busybox if the base install already comes with full gnu coreutils? I remember Debian as the distro that Just Wroks(TM), when did it all go so wrong? Is anyone else here having similar issues, or am I doing something wrong?
As everybody else has said, Debian is working as intended. To respond to the actual post though, Debian is working exactly as it always has.
If you think Debian used to be good, you must really love it now. It is better than ever.
Unlike in the past, the primary drawback of Debian Stable ( old package versions ) has multiple viable solutions. Other have rightly pointed out things like the Mozilla APT package and Flatpaks. Great solutions.
My favourite solution is to install Arch via Distrobox. You can then get all the stability of Debian everywhere you need it and, anytime you need additional packages or newer packages, you can install them in the Arch distrobox. Firefox is a prime candidate. You are not going to get newer packages or a greater section than via he Arch repos / AUR ( queue Nix rebuttals ).