Show us the way to coffee nirvana...The problem is that the blender does not let the pieces "drop through" once they have reached the desired size. A certain percentage of the coffee gets ground and reground and reground yet again, into "fines" like talcum powder. These fines add to the bitterness.
I didn't quite understand this, and used a blade grinder for years. What a difference a burr grinder makes! I am freaking serious. IMO, the two best things you can do to improve your coffee (after you have decided to go whole bean and purchase good coffee), is to get a digital kitchen scale to make sure your ratio is right, and get a burr grinder to reduce/prevent fines. Makes the most difference, best bang for your buck.
All the other things matter, but matter far less IMO. What I mean is that, for example, worrying about brew temperature (as you can with some of the higher end drip machines) IMO is a ridiculous waste of time if you don't have the water to coffee ratio sorted out, or are using a blade grinder. My experience going after a pour over technique but using a blade grinder, one is missing so much that is lovely about coffee flavor, and kind of just re-arranging deck chairs on the Titanic.
My opinions entirely YMMV everyone's taste is different. A stove top percolator and Carnation evaporated milk makes coffee that won world wars, so to each his own.