I think Signal shot themselves squarely in the dick by removing SMS functionality.
Previously, you could use Signal as the primary SMS/messenger app. Any conversations with other Signal clients secure. Conversations in SMS/MMS? Marked as not-secure.
But, out of some purity concerns, SMS functionality was removed and the dev team focused on adding useless shit like “stickers” and then the pin-code harassment.
Signal adoption plummeted as intended (?)
And that irony now is that messenger on Android is RCS compliant and currently has this exact functionality, except it’s less trustworthy.
Once again I’m using one messenger and everyone else who’s using an RCS messenger gets encrypted, but SMS (clearly marked as such) is a viable fallback.