The iPhone X also had smooth rounded edges and was small by modern standards (bigger than the 3GS, though). Still one of my favourite iPhones.
Most people now days put their phones in protective cases, so the sharp edges don’t matter too much. And if anything, it makes the cases easier to design and smaller/thinner.
The iPhone X was better than the 6-8, I think the screen filling the whole thing helped it out, but it was still too large for my liking. I moved to the mini when it came out to get a smaller phone.
I found it interesting that the intro of the Duo talked about how it had 90% of the screen of the iPhone 18, as a way to talk up how big it is. They didn’t do this for the iPhone mini, and I think it’s why it failed. The iPhone mini screen was only .1” smaller than the 8 Plus, in a form factor that was smaller than the normal 8. I think selling it like that, as the base level iPhone (without the mini label) would have made it a success… but I’m still bitter they killed it off.