We'll never have the luxury of laser-trimmed resistor or matched transistor, an integrated opamp usually outperforms discrete designs, at least for low-power applications. But yeah, it's much fun to build an integrated component from scratch and see how it works.

BTW, NwAvGuy, the audio guru who have vanished, has some interesting criticisms on the dismissal of opamp in the audiophile community. https://nwavguy.blogspot.com/2011/08/op-amps-myths-facts.htm...