They are just too late to the party, this is not exclusive to them but all new vtubers specially corporate ones. So most of the content they do is the already established or has been refined in execution, not to say it cannot be improved anymore. They also not willing, at least for now, to do something out of ordinary maybe because as corporate vtubers they also need to handle the paperwork.
life consultancy, old games, surprise collabs, inter company tournaments, gimmicky karaokes,asmr,cooking stream they are all existing genres or acts that most v tubers/streamers do nowadays however some of them stand out more than the others.
An example would be Leos and korone approach to old games as an example. One is a more meticulous show on how to beat a game while entertaining the audience and the other is just a rather blind play trough while showing genuine amousement and love for the aspects of the game that appear and endears the audience to keep watching those reactions.Both have different personalities and approach and people find that unique on them.
As a streamer putting your personality and twist into your game play or content is the goal.
Nijien hasn't had that yet imo, they are not know for something specific or way to play . mostly their difference is rather on their quirks like selenes laugh or some jokes like it was kiara bottom left or im pomu. Whatever content they choose to stream with is irrelevant, what matters is what they do to stand out with it. streaming nekorpara,onimusha or little nightmares is no different from streaming toki memorial, dmc or soma.
The again Op is baiting with weak bait so just chose to give a more serious opinion on how is gonna be harder for future chubas to stand out.