Ah, I see. Your point isn’t necessarily reliability but availability. It’s an interesting perspective to hear that the US appears to be so behind (at least from a European perspective of course) when it comes to messaging apps. As far as SMS reliablity goes, I have occasionally had messages not send, or have messages come in delayed considerably. Or stuff like 2-factor auth texts not coming in, requesting a new one and then suddenly receiving 3 at a time. Not deal-breaking or anything, just the occasional annoyance.
I don’t think WhatsApp allows you to send a message to someone who doesn’t have the app. So WhatsApp would just inform you. Although I don’t recall the last time someone did not have either WhatsApp or Signal installed. But again, that appears to be far more common in the US?
Do you ever miss the extra features that web messaging brings, like in-chat polls, voice messages, etc…? I’m not sure how much of that RCS supports (because almost nobody uses that here). To me it seems like the convenience of web messaging outweighs the “does person x have app y” question, but that’s probably because I never really have to ask myself that question.
I also just realised that you state that everyone has SMS messaging. There are phone plans available here that don’t offer SMS messaging anymore. You can still receive them, but sending them either doesn’t work or costs a high premium (obviously this disadvantage is offset by a lower price for the rest of the plan). I wouldn’t be entirely surprised if SMS eventually just gets phased out.