Electret mic reads nothing but noise

I’m having some issues trying to process sound on my ESP8266 NodeMCU using a standard electret microphone (Electret Microphone Amplifier - MAX4466 with Adjustable Gain : ID 1063 : $6.95 : Adafruit Industries, Unique & fun DIY electronics and kits). The circuit is as simple as possible - 5V wall transformer connected to the wall powers the microphone, with the output directly into the analog A0 pin. Code is simply reading Serial.println(analogRead(A0)). This outputs the attached noisy signal.

Not only is the signal noisy, but it picks up almost no other sound. Only when banging the mic on the desk or tapping it directly do I see any sort of response. I’ve adjusted the potentiometer in all directions with barely any effect. I’ve tried a total of 3 identical mics and all are like this. I’ve tried multiple ESP boards, so it’s that.

Are these mics just terrible? Am I doing something wrong? Do I need some caps to reduce noise, or resistors somewhere? Most diagrams I’ve seen don’t include these. Any advice is appreciated, thank you!

Am I doing something wrong?

Well yes. You describe your circuit then you talk about adjusting a pot, giving us no idea of what this is doing.
So off to the link that you have not posted correctly. In future use the link icon 12 from the left in the reply box, looks like a chain because copy and paste is tricky on a mobile device. And we find you are not using a microphone at all but a breakout board that contains an amplifier.

From your description of your setup it seems you don’t have a common ground between your wall wart and the Arduino. So wire one up.
As stated on the product page you are best powering this from the 5V and ground pin of the Arduino.

Are these mics just terrible?

No, but being small they are less sensitive than a studio mic which will have a much larger
electret or dynamic transducer at its core, and a very carefully designed acoustic housing.

First check that the unit has all its connections solid (check its getting power with a multimeter
on voltage setting).

Then post your code, since we don't know whether the problem is hardware or software
related at this stage.

You need an amplifier for that mic. The signal is too small otherwise.