Are you talking about Fortnite in general, or the Battle Royale mode?
The weird thing is that my impression is that Fortnite was talked about for awhile as this Horde-mode construction game, sort of like minecraft meets L4D. Then the BR F2P mode was added and the whole thing blew up.
Summary of video games in the last 5 years.
H1Z1/Rust/etc are all a continuous survivalist game and other games were mostly mods.
I'm personally excited to see where Activision or EA take the genre (Blizzard too but I don't see that happening anytime soon).
I guess they can't complain about the success but it would have to feel at least a little bit demoralizing.
I just had the impression DOTA was made by some guy who wanted to make something like DOTA and Fortnite was made by some people who wanted to make some mix of L4D and Minecraft, but pivoted to doing something like PUBG instead.
As far as I know the regular mode is not free to play.
I only tried it because it was a free alternative to PUBG