Feel free to delete any of the spoilers, I'm not going to go in depth in them but they are kinda spoilers.... I'm also going to mainly approach this as an older account going to GWI. TLDR on that front: It is interesting and everyone should do it once, but needs to be simpler to leave for those teleported there. As I've written it, this is quite spoilery but I am sure I have something wrong so please correct me!
For new players, I don't think it is a good impression having them start on an island with nobody else nor a story to keep them interested at the moment. I like how it teaches core mechanics, hell the combat option looks interesting, looks like they even need to learn about what abilities/targets do and their signifcance. I also don't think it is a good idea to keep them on there too long, smacks a bit of the old freemium game model of making you wait, although I appreciate that is not it's intent at all. Why not kick them out after a week and make them figure their way back in if they want to fully explore the mysterious island?