My son is 9 and it is his new go-to game (used to be rocket league). He's won it twice and my god was he chuffed the first time.
Quite incredible how quickly these kids can build. That's all too complicated for me so when I play I just follow him and treat it like PUBG (hide!).
My son loves it. I'm alright at it but I'm very crap at the building side of things. When you start shooting someone and they quickly knock up a wall around them it's pretty frustrating!
I like PUBG because there's no building involved, and vehicles - but enjoy the cartoony-ness of Fortnite...