Check out one of the privacy-focused Firefox forks like LibreWolf, IceCat, or Waterfox. All three disable/rip out pocket by default, I believe, and reduce number of situations they phone home to Mozilla or Google. Memory savings are minimal though.
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.
Librewolf is one of the more prominent ones these days. There's also Waterfox, which is based on an ESR (so, older) version of Firefox and likewise fits the bill.