"Firefox version 115 is the last supported Firefox version for users of Windows 7, Windows 8 and Windows 8.1."
That's a version from over 2 years ago.
ESR version doesn't mean it has never received changes for 2 years.
The problem is not the lack of patches. The problem is with websites refusing service based on client's version from the user-agent or breaking by using cutting edge features without a polyfill.
Chrome dropped support two years ago or so.