Why can't my desktop sync to my mobile phone data instead of me having to store, delete blah blah blah

You need to enable me to sync the desktop to my mobile phone. I've had mozilla firefox on my Mac and android phone for years but now I am expected to work out how to create a back up and then delete all of my data and trust it will upload to the new browser on my desktop -- which before the update held the same data. Really unimpressed. Get it sorted.