It’s usually not. I have one old car with a CD player and a less-old car with a USB stick loaded with media. The flash storage is better.

But if you have nice speakers and listening space, the quality of the DAC matters, and a real CD player would probably have a better DAC and sound better than compressed audio on a flash drive sticking out of your receiver. Unless you have a fancy audio server/DAC setup, in which case it’s moot.