Microphone quality is really poor in my Macbook pro 2018 (15 inch) when I compare it to Macbook pro 2016.
When I enter Audio MIDI Setup on Macbook pro 2018 I see (sorry for polish lamguage):
However in Macbook pro 2016 it was:
Is it OK for my Macbook pro 2018 (15 inch) to have only 1-in ?
This seems normal.
Looking at the tech specs for both the 2016 MacBook Pro and the 2018 MacBook Pro, you will see under the "Audio" section, that they have 3 microphones and 2 microphones respectively.
So, it appears that the 2018 model has one less microphone channel and this is what you're seeing. As for audio input, I would look at getting a quality USB audio DAC instead of using the built in microphones