It's weird. With every single app having a DM feature years before Whatsapp was even invented, with every single cell phone having email and SMS capabilities, and with a bunch of E2E encrypted apps already in service, why would I want to go back to Facebook's ecosystem in 2023?
When every single person you know uses Whatsapp, you have to use it too. That's what this law is about. So you can use other apps even if everyone else uses whatsapp
Whatsapp worked on iPhone, Android, Blackberry and even some old ass java phones
They dominated the market in most countries or were close second to Messenger.
Now they keep growing and it doesn't give any chance to smaller better apps, this law makes it possible for you to use only signal but also chat to people that only use Whatsapp