WhatsApps main “killer feature” was being early in the market to quickly reach a critical user mass.
Doesn’t matter which competitor, people will install an alternative, see that only 5-10% of their contacts have it and will immediately uninstall.
I see potential in preinstalled messaging apps. But it needs to be cross-compatible between iOS and Android. Otherwise it won’t fly.
Well, you pay with your data so there’s that…