French press brewers are great and nothing to be ashamed about using. There are two big variable that you can tweak when using it, the grind size and the time

French press brewers are great and nothing to be ashamed about using. There are two big variable that you can tweak when using it, the grind size and the time you keep the coffee brewing before plunging and pouring. Water temperature is a third variable but with a basic kettle don't worry about it and just use water off a boil. If you decrease the grind size it increases the extraction, and if you brew for longer it also increases the extraction (to a point). When you get wildly different results from the same beans it likely means you've changed one of those variables. Try playing around to find a good balance of grind size and time brewed. I usually like a kosher-salt level of grind size (moderately coarse) with a 4 minute or so brew time. But if the coffee comes out too bitter then I likely over-extracted it and increase the grind size or reduce the time brewing, and if too sour then it's probably under extracted (decrease grind or brew longer next time).