WW
It's like a guitar. Good guitar, good tone.
Bad coffee/bad coffee.
Get a bag of decent ground coffee and you should be fine.
Wife likes to heap the 4 tablespoons too high "likes it that way", makes too strong a coffee, not as pleasant to drink.
Decent water, decent beans, decent coffee.
I sometimes type for 20 minutes instead of pressing the plunger down, I sometimes press it instantly just enough to get a cup, results are usually about the same, good coffee.
Something I learned in Seattle in the early days of the coffee craze from Illy Cafe sales people and barristas is that strong coffee should never mean bitter. Bitter is another problem, probably over roasting.
We use Craven's Earth & Sky blend, reliably great coffee, morning after morning. I keep an extra bag cold in cellar but not frozen. I also put it in a ziplock before use, and between uses.
I use an ancient Braun grinder stuck on Espresso, too fine for drip or press, doesn't seem to be much of a problem unless overheaping the measuring spoons.
Try a dark coffee like French Roast from a reputable coffee purveyor, and filter the tap water, and your coffee should improve markedly.
There's always Earl Grey, but to me it doesn't have the same kick.