Burrs, blades & fines

A blade grinder is a propeller in a cup. It does not grind; it chops, randomly, so the output is boulders and dust at the same time. In the brew those two populations fight: the boulders under-extract and taste sour, while the dust over-extracts and turns bitter. The result is a cup that is somehow harsh at both ends — and no recipe change can fix it, because no single grind setting exists.

Burr grinders crush beans between two cutting surfaces held at a set gap. Nothing leaves until it is smaller than the gap. That single mechanical fact is what you are paying for: a population of particles that mostly agree with each other.