My 9 year old plays it. So does his entire friendship group in Year 5 Juniors.
It’s more addictive than Minecraft and Roblox because they have to keep playing in order to ‘tier up’, and the game has big updates where new weapons, skills, map locations, etc are added and if you miss the update, well, you’re just not cool at Fortnite or something.
It didn’t get my attention at all and I play various video games, it really is ‘made for kids’ despite the high PEGI rating and adult-age fan base. My son said he and his friends only found out about Fortnite because DanTDM the famous kids Minecraft YouTuber progress onto it and became obsessed with it. Don’t underestimate the influence of kids youtubers 
Yup, your son can play as a latex clad busty, booty, weaponised avatar woman, but it’s all harmless stuff. He knows the difference between fantasy game worlds and real life.
It’s not the content, it’s the fast pace, colours, competitiveness and requirement to constantly progress within the game else you lose out, that keeps kids brains addicted.
He’ll likely go onto other video games as he gets older, or may find something else. I think I quoted elsewhere that the gaming industry is now worth more than the music and film industry combined. It was on the news a few weeks ago. It’s worth billions the news said.
My kids still do craft, art, clay modelling, reading books, (occasionally...) play outdoors, mainly because they don’t live near any of their friends mind you. But I see the mood changes and addiction when they play video games, and just have to work with that to moderate it.
I still remember hiding under my quilt with a green glowing Star Wars light sabre in 1977, using the light to read a book with 
. Times and technology have changed, just have to work with it I suppose.