I bought a new Mac for a secondary computer, particularly for my wife to use, and she was driven crazy by ads in just one hour of browsing on Safari without a proper ad blocker. Adding an ad blocker to Safari required using an Apple account which she doesn't have and I didn't want to use it for mine (never plan on buying NERFed apps from the NERFed mac app store which is 99% spam anyway) so I switched her to Firefox which lets me add an ad blocker without signing in.

Make her an account with throwaway everything or switch her to a sane browser, as you did :)

FWIW wBlock is on GitHub and can be used without an Apple account. I’ve found it to be excellent.