The ADCs on the ESP32 are similar to other embedded MCUs in that they are not intended for audiophile-level audio capture, as some people seem to think they should be capable of.

The main value proposition for these ADCs is to hook them up to a simple potentiometer to allow physical input controls, and even for that purpose you need to average multiple samples to get a somewhat steady value. Of course the ADCs can be used for various other tasks, but "ADC" does not mean they can do anything any ADC can do, there's a wide variety of quality and purpose in the field of ADCs, and the ESP32's ADCs are a cheap and easy way to add a simple ADC function to the chip.

I have been able to use the ADCs quite easily for input controls and monitoring slow-changing voltages, in ap;lications where abdolute precision wasn't the goal, it works perfectly fine for that.