SMS has always been unreliable. It has no place in modern communications.
No delivery confirmation: messages silently drop and the recipient is unaware you attempted to message them. There is no notification to you that your message failed to deliver.
Profoundly long delivery delays: messages sometimes get stuck and get delivered hours or days later. "Hey dude meet me out front" delivered 16 hours later, etc.
Length restrictions: some phones still do not handle long messages correctly. If the character limit is exceeded, messages are cut into unordered pieces, or the message is truncated and part of the message is simply deleted.
I'm not saying RCS is the answer, just pointing out that SMS is garbage.
Maybe some hardware/carrier configurations have less problems?
All I can say is, in the past 15+ years of SMS messaging, in the US, on every carrier, with devices ranging from the early Nokias to the latest iPhones, I have had reliability problems that are frequent enough for me to avoid SMS when possible.
It failed for over a month for me, but only in one direction, and I didn't know. Other party thought I was ignoring them. Lack of confirmation makes it 'worse than useless' in the failure case
No delivery confirmation: messages silently drop and the recipient is unaware you attempted to message them. There is no notification to you that your message failed to deliver.
Profoundly long delivery delays: messages sometimes get stuck and get delivered hours or days later. "Hey dude meet me out front" delivered 16 hours later, etc.
Length restrictions: some phones still do not handle long messages correctly. If the character limit is exceeded, messages are cut into unordered pieces, or the message is truncated and part of the message is simply deleted.
I'm not saying RCS is the answer, just pointing out that SMS is garbage.