Fair enough, I'll give it a go.
Unlike most shooters, Fortnite's weapons are extremely ineffective and useless. Especially on long-range. This encourages more amateurs and young people to play it, making it more casual.
The cartoonish characters, models and animations are also meant to draw in this mentioned audience, much in the same way as TF2 and Overwatch.
The "building" feature further proves this, as it's obviously a direct inspiration from Minecraft to appeal to this audience.
Unlike most other shooters, you are discouraged to rely on your aim and in-game IQ, due to the first mentioned variable, and due to the building feature of the game.
Basically, the game is a mix of the most popular games on the market for children, excluding RTS.
I'm glad that the children have a game that they enjoy, especially since it decreases their numbers in other games that I enjoy, but I just don't think Fortnite is a good game due to the mentioned facts, and I doubt it can survive as an esport at all.
I don't personally have anything against the Battle Royale theme, I'm just waiting for a proper game that isn't filled with horrendous bugs and glitches (PUBG) and has useless weapons with a kid's theme (Fortnite).