I don't really have a problem with DACs on PCs, but the amount of noise present on most motherboards is terrible. (I can usually tell when my machine is compiling).

A few years ago I bought some USB DACs and separate headphone amplifiers and it made a world of difference, even to my relatively ancient ears.

At least the iPhone's DACs are absolutely audiophile quality, especially because the idea that "an audiophile quality DAC costs 20x what you see in smartphones" is patently ridiculous. There's no evidence at all that any good as in not flawed DAC will sound the same on nearly any, if not any system.

At the very least, the audio quality degradation of most bluetooth devices has a worse impact than even your average middle tier Android phone's dac.