I think the age does make a big difference. I'm about 40, and I've rarely heard this IRL among people near or older either. The people I've heard it from were mostly in their teens or early 20s. Some 30s and 40s have admitted to leaving friends or family out of group chats because they were on Android though.
But that said, how do you know nobody stopped talking to you because of it? One of my friends (who is early 40s) said his family started leaving one of their family members out of the group chats because it "degraded the whole experience" and I doubt he ever told the person he was being left out, let alone why. I would imagine it's kind of like telling somebody that you aren't going to date them anymore because they're not attractive enough. Not something you want to admit, and even though it obviously happens, I've never heard of somebody actually being told this.
Most of my friends are in their 40s/50s. No one knows what iMessage or RCS even is if they have an Android or iPhone. WhatsApp spread like wildfire here because no one gives a shit :)
Maybe I've been kept out of group chats, it is annoying group chatting an imessage thread with android in it. I forget what it does but something is strange about it, but I'd definitely remember if someone I remotely cared about talking to just ghosted my SMS one day. I can't think of that ever happening. I had tons of friends in my 20s and almost none of them ever used Android. It was mostly tech people I knew that used Android.
But that said, how do you know nobody stopped talking to you because of it? One of my friends (who is early 40s) said his family started leaving one of their family members out of the group chats because it "degraded the whole experience" and I doubt he ever told the person he was being left out, let alone why. I would imagine it's kind of like telling somebody that you aren't going to date them anymore because they're not attractive enough. Not something you want to admit, and even though it obviously happens, I've never heard of somebody actually being told this.