ok, let me explain more, each company/brand have to make decision what they should do and what they should give up when develop a new products,
I think Apple can easy make the best sound quality DAP but it means less battery life, bigger size , expensive price , and yes, hotter, they known they are not going
to sell someone like us that take sound quality ahead everything. at the other hand, some brands, they trend to make the best sound quality not matter the battery life,
cost, and heat. for example, Sony‘s PHA-1 , the battery life is only 5 hours, do you think Sony lack of the ability to make an DAC/AMP which have 100 hours battery life?
Another issue about the UI and the firmware, I don't think iPhone can be so great if it can supports so many kind of music, photo, video, in fact, the iTune done almost 90% jobs to convert everything to the same format in PC/MAC, just compare IOS with Android, you got some and you lost some. there are not magic in the world.