[Stratoscope]

Coffee shouldn't taste bitter. Bitterness generally indicates that the grind is too fine for the brew time. Short brew times work with finer grinds, long brew times with coarser.

As an example, I'd used an Aeropress for years with a rather fine grind (finer that typical drip, but not as fine as espresso) and short brew time. (For Aeropress aficionados, I was using the regular method, not inverted.) The coffee was always smooth and never bitter.

Then I got a Clever Dripper (highly recommended!) which typically uses a much longer brew time. I started with the same fine grind and it was coming out bitter. So I increased the grind size to more of a typical drip grind (and slightly on the coarse side of that), and it fixed that problem.

The Clever Dripper also uses much less coffee (again because of the longer brew time), and it pretty much replaced the Aeropress for me.