I understand they want to create a lot of game modes, but unless you are steadily growing, you are just further and further segmenting your existing userbase and risking it all. And to be crystal clear, I am not saying the sky is falling, Fortnite is DOOMED, but I don't know where they go from here as they already had to walk back from some of the monetization of in-house made modes and tone down how generous they are with third-party made modes. They killed off rocket racing and I am unsure the longevity of some of these other modes to be officially supported rather than proofs of concepts
I guess there is technically some third parties who had announced they are making full games within Fortnite or UEFN, that is probably going to be the next big highlight if these start to hit this year as I cannot imagine Epic should continue to release their own in-house modes based on their current performance.