You definitely shouldn't invest time in SMS. Without RCS (or some custom messaging protocol support), "texting apps" are pretty much a dead market.
RCS is both more secure and more user friendly than SMS can be by design. Once the iPhone gets RCS support in the coming months/years, this will be especially true.
If you message cross-platform from Android to iOS, and you can't get everyone to agree upon a 3rd party app, then you're kind of stuck with sms. This isn't a problem that is going away in the near future. Apple relies on their locked messaging platform to influence their users into thinking iOS is the best. The users then pressure all of their friends to get iPhones too. It's an effective strategy for them. Very few iPhone users seem to understand the games being played.
You're right, I've updated my reply... Hopefully someday that will be a generic RCS feature not exclusive to Google and/or Apple and Google will work to make the E2EE work between their two systems.
Plenty of services still unfortunately rely on SMS for 2FA, so we'll still need a client to receive them. Doesn't really need to be able to send them though, I don't think any human has sent an SMS message deliberately for about 12 years!
I'm happy with my version of simple messenger, I've not updated it for a while... Am I good to keep using that? Can you explain more what you mean by selling out?
The lead dev sold simplemobiletools to Zippo Apps (or whatever they're called), a company known for buying apps and stuffing them full of ads, trackers and bullying people into buying subscriptions.
That news came a bit out of the blue, and while I understand why he sold it, the fact that he sold it to such a fuckface company that goes against everything his apps stood for is... yeah
That is the one selling out. All "simple" tools where sold to an ad firm, the f-droid version is probably fine for now but if you got it from Google play : run.