Coffee that tastes like burnt cellulose (not as you imply cellulite lol) has been left on the warming plate too long. It’s like complaining that tea tastes metallic and bitter: sure, it does if you do it completely wrong.
If you want to make good coffee, you need to use beans that haven’t been roasted too dark, then make it with the right parameters for good extraction, then put into a cup immediately and drink. Just like you shouldn’t warm up tea for hours before drinking it.
Great coffee can be drunk without milk and gone cold and it will still taste like some kind of strange and intense and delicious cherry tea.