It seems like smartphone screens are getting bigger and bigger. So, is this a mission to ux design? What’s your opinion about it?
Eh, not really. To me, it’s just another flavor of responsive design. I don’t see there are any unique or novel problems involved.
From a development standpoint, yes. From a UX standpoint, not really.
You can operate a small smartphone with one hand while holding it in the same hand. An iPad, with both hands in a different position.
A big smartphone will require you to use it with one hand, while holding it with another. This is why, from a UX perspective you get new challenges. The patterns that you use for the smaller screen do not all work on the bigger screen. And the same thing is applicable to the tablet patterns.
I’m curious what you’re basing that assumption on.