To keep a thread from being derailed, here's a more specific breakdown of how Fortnite has been deemed problematic by gamer parents.
Or at least, the gamer parents I communicated with.

This game wasn't really on my radar until this conversation was started, then I became more then a little concerned.

The first person was commenting on how their offspring was wasting all their allowance and earned money on Fortnite's ingame store.
The second person then came in and explained they'd had to lecture their nephew about deceitfulness because they were scamming money from all their relatives to pay into the Fortnite ingame store.

Both these people then told me exactly what was being purchased, emotes and outfit customisations.
These things have no practical benefit ingame (in terms of improving gameplay), yet apparently a fortune is spent by the junior playerbase in acquiring them.

Much later, I communicated with a 3rd gamer parent and related the highlights of this conversation to them, to which they responded that their own children have become so focussed on Fortnite that when their parent tries to get those children to play any other game, the attempt is completely ignored.

From my perspective and most likely, those of the gamer parents I communicated with, Fortnite is encouraging an addictive like obsession in their junior playerbase, one that is causing them to spend money to do so.

That's why I distrust this game so much and get annoyed when I see the Fortnite toys/merchandise for sale, it's promoting a product that is encouraging self-destructive behavior.