Jokes aside, I don't think matrix/element, at this stage, are trying to overthrow telegram or whatsapp.
It seems their main approach is somewhat aimed at the people who use(d) IRC on the general audience side and institutional clients who they work with to create ad hoc solutions for employees, in which case which client to download is slightly less problematic since it's going to be a custom one anyway
It just so happens that right now it's easier to land with folks who are patient with sharp edges and already believe in the value of FOSS, E2EE, and decentralization. Gotta start somewhere, right? :)
IDK if you caught it, but the project lead, Matthew Hodgson, gave a main stage talk at FOSDEM a couple weeks ago and offered an update on the project and, in particular, on how we're taking advantage of the push that regulators are making for interoperability. WhatsApp, in particular, gets mentioned in this context and the writers at WIRED and Tech Crunch seemed to pick up on that!
Perhaps a technology will not have success if its users need to do basic reading.