I think Waterfox is what you’re looking for. Or LibreWolf. Be aware that streaming services may not work due to DRM.
If pocket is your biggest issue, you can disable it in about:config on Firefox, just search for “pocket”. There’s a boolean for pocket integration. Double click to toggle and you’re done. I’m on mobile atm so I can’t get you the correct keys but it should be self explanatory once you get to that stage.
Optimized version of Firefox? ( fedia.io )
Is there an optimized version of Firefox that removed Pocket and other unneeded features? Does it use less memory?