while this is an attempt to disrupt monopolies of Whatsapp and such, I'm quite wary of it. if I'll use another messaging service to message someone on Whatsapp, Meta will most likely still collect all the metadata about our conversation, and I bet that's going to stop Signal, my IM of choice, from implementing it.

and besides, it's going to make it more difficult to make people move away from Whatsapp, since "you can already use [the IM you use] to message me".
I'd rather wish it would force the big players to open up their APIs, so people could create alternative clients. I'd love a less bloated and better designed app to contact people on Whatsapp, with all the community and status update bullshit ripped out.