there are many problems with mobile devices these days:
I dont need a 2k display on a 5-6" phone!!
i dont need a 4k Tablet/notebook!!
only on a desktop monitor 2k/4k makes sense but not on mobile devices.
the real problem of mobile devices is the batterylife.
wouldnt it be better to focus on more efficient 1080p displays, instead of getting more and more pixels (wich your eye cant even see anymore) into small phone screens?
another problem is: LTE. why is it a problem? because its useless thats why!!
you get extremely high speeds with it (i get 50mbit down/up) but what can you do with that? nothing!
LTE eats so much battery you cant do much with it. but before your battery dies, your provider hits the brakes after you hit your tiny little datacap. (i pay 15€ per month and get 3gb unthrottled data over LTE and after that 64kbit wich is ridiculously slow. 15€ sounds cheap but i only got internet with that, no call/sms flatrates and no free phone)
seriously? instead of throtteling it to something like: 1.5/2mbit wich is still usable you go as low as 64kbit? you think its only my provider that does that? nope ist standard in Germany.
there are many, nice online services for mobile devices, like movie/tv and music streaming services.. all useless because of low data caps!
you got your nice 2k display. how many 2k videos can you stream with a datacap of 3gb? 1 per month? and you cant even watch it Completely because your battery dies halfway through the movie.
theoretically a smartphone is smart, but most of its awsome features, are locked down by the providers, and by its battery.
unless those 2 things change, all that a "flagship" smartphone is, is a 600€ phone/sms/whatsapp and social media machine, something a 100€ smartphone can do just as good.