I just skimmed this page and I feel like Fortnite has somehow become Destiny:-
Daily/weekly challenges
Secret missions and boss fights
Focus on cosmetics and loot
Tons of levelling systems
Community resources (e.g. maps, boss guides etc) are "needed" to play the game
Not saying ti's good or bad, just taken by how much similarities there are in two successful GAAS games.
As a former 'hardcore' Destiny player;
I'll give you the Daily/weekly challenges, but these are a bit easier (and quicker) to complete than Destiny's.
The secret missions not so much, it's literally "Go place A, OK you did it." The Boss fights however, yup - 100% Destiny.
Cosmetics were always the name of the game, but now it's popular, there are more tie-ins so you're hearing about it more. Loot; not so much - the coins are just ways to level up that you come across whilst playing.
Levelling systems are essentially: Play the game. You get XP for a bunch of different things, though I wouldn't call them separate systems like how other GAAS handle it.
Community resources: yes - but its a big island and the age range for this game skews younger, for some kids it's their first game, so I understand if they might need guides for some things.