Re: "Why can't we have a phone that has all these decent specs"
...perhaps because those 'decent specs' require a bigger battery and battery size is constrained by screen size? There's a reason all the 'S' versions of flagships have lower specs, not just a smaller screen. How much battery time do you want to sacrifice and/or how much fatter do you want the case for a thicker battery (in a world that overwhelmingly wants thin phones).
Or maybe you don't need a flagship and the problem is imaginary.