Bitterness belongs to coffee's flavor vocabulary and is not automatically a brewing fault. Some drinkers enjoy its contribution in dark-roasted coffee or espresso, particularly when it sits alongside sweetness and texture. The question is whether the cup feels balanced to you.
An unpleasant bitter impression can have several possible contributors, including roast character and extraction. Avoid treating a bitter cup as proof of one particular grinder setting. Astringent dryness, sourness and bitterness are different observations, even though they may occur together or be described imprecisely.
Keep the coffee and brewing recipe constant while making one adjustment. Record grind setting, dose, water quantity and time so that a change has a clear reference point. If the roast itself is much darker than you prefer, changing beans may be more productive than repeatedly forcing the recipe in the opposite direction. Describe the finish in concrete terms: pleasant cocoa-like bitterness, sharp harshness or persistent dryness. That vocabulary makes comparison more useful than labeling every strong-tasting coffee bitter.
The conversation
A good question can make a better brew.