I know the article comes from Mozilla (of course they were founded to help slow down big brother, not digest you like Microsoft, or Google),
BUT
There are facts there in the article, that point out the differences and if you think Mozilla is lying, you could verify those shortcomings in Safari yourself.
Opinion is one thing, facts are another. Of course these may be fine points in security and functionality you don't care about.
Also don't forget the much richer plugin library available in FF. Of course the leader worldwide is Chrome... by a long shot... but I try not to use stuff by the people who sell most of your data, Apple, Microsoft, Google, etc....
Greg
p.s. Safari scores very low on HTML 5 compatibility also, lower than Edge, Firefox, and Chrome.... as flash is end of life this month, all those sites are changing to HTML 5.