No-one seems to be building such a phone, probably because most people in their 70s and above either don’t have a cell phone, or still rock a low-tech flip phone with physical buttons.
My own father (83 this year) would love a low-resolution screen the size of the iPhone Pro Max, just without the bells and whistles and “Pro” aspect of the Max.
Hell, if the iPad mini could be turned into a fully-functional cell phone without relying on VoIP hacks, he’d likely jump at that.