> Where do you live that WhatsApp is essential?

In Brazil, for example, without WhatsApp you are an outcast of modern society there, businesses communicate with customers on WhatsApp, whole families and friend groups only use WhatsApp.

> WhatsApp only has value because of the network effect. Quit the platform and make your contacts find you elsewhere. Every platform dies eventually. The users just need to leave.

The network effect is exactly what makes it really hard for any single user to decide "I'm leaving" and tell every single person they need to be in touch to contact on another platform they don't use. What you are suggesting is simply impossible on an individual level, the only way it happens is if the platform has major issues that bleed users because it isn't working or the platform is made inaccessible by the government. Even a better competitor appearing will have a very hard time to crack the market share of a established network exactly due to network effects.