- Fortnite is not a shooting game. This is the main trap of the game. It looks like shooter, feels like a shooter, can be played like a shooter, but is not a shooter. Fortnite is a fighting game and should be played like one. It has an incredibly heavy reliance on mechanical skills (ala fighting games) and failure to recognize this will just lead to disappointment with the game.
- Fortnite's success was a complete accident. The BR mode was a spun off "weekend project" for fun in order to attract players into buying Save The World. It was free and meant really just as an advertising tool. There wasn't much thought put into how it was supposed to play, but Epic 100% did not see where this was going, nor did the community at the time. And that was very much instrumental to it's success. Had Epic saw this coming, they would have totally destroyed the mechanics that made it so good right off the rip. I could write an essay about this, but the short of it is that the building mechanics were used in a totally unintended/unforeseen way and it lead to a wild success. Mark my words, one day in the future, free of NDA's, former devs will come out with some truly wild stories about FNBR.
- Fortnite became a runaway success with kids because they have the easiest time adapting to completely new game mechanics. It gets a little gritty here, but the short of it is that Fornite is a completely new type of game with a completely new type of play style. Older players were trying to shove a square piece through a seemingly square hole (see note 1 about shooter/fighter), while younger players could easily adapt their blank gaming slates to fortnite's play style. Yeah the cosmetics and stuff helped, but nobody likes playing a game they suck at.
TL;DR: Fortnite is deceiving in what it is. Fortnite was a total accidental success, because of accidentally awesome mechanics. Kids love fortnite because they were less prone to that earlier mentioned deception, and can pick up new things much quicker than older gamers.