That does sound awful.
I am longtime Firefox faithful. But I keep extension usage down to minimum- multi account container, ad block for YouTube, leechblock, clear url, zotero and fpl tools (fantasy football) right now. Tbh Firefox rarely bothers me nowadays with resource usage. I am confident I haven't had to restart Firefox since last November.
My work laptop is a Lenovo P52 with 32GB of ram and win10. Home laptop is a Lenovo legion with 16GB of ram and win11. I had so many issues with performance in the past that I just trained myself to never keep resource-hogging stuff running in background that I am not actively using.
I regularly have zoom and Firefox running while playing MMO games on home laptop. Firefox, SQL server etc. running in background while running multi-core data analysis on work laptop. I never had issues with Firefox, and if there's a memory crash I usually know what caused it. But it is down to hardcore discipline using the machines, and I understand it is not usual patterns for others.