What are your specific concerns? I could list things like: lack of bold and italic , poor voice message UI, lack of video conferencing , lack of group names, ...
Note that WhatsApp was wildly popular for over half a decade before it got most of those features.
In other words: I don’t get the point of talking about these cosmetic blemishes. * Signal today feels like WhatsApp at its inception. I.e. a messaging app with the potential to be used by everyone and their dog.
Or is there some fundamental problem you’re encountering that I’m blind / oblivious to?
* edit: let me clarify: “... talking about these cosmetic blemishes as if they’re fundamental blockers to adoption. “