Mmm? French press is generally considered the easy way to get smooth, inoffensive coffee.

I'm gonna guess you were using a nasty-ass grinder, even a ... eeww... blade grinder?

A poor grinder, and anything with a blade, will create different-sized grinds, which means the smaller ones will over-extract and go bitter before the bigger ones have released their full flavor. The lack of paper filter means you WILL taste that, because FP coffee gives you everything the coffee has to offer. Drip or percolator coffee with a paper filter will remove most of those intense, bitter oils - but also removes much of the coffee flavor with it (and I can often taste the paper).

The press is indeed awesome for simple and cheap, but it really does demand great, fresh beans and a good grinder. That's not me being a snob; i'm just agreeing how it's easy to end up with bitter coffee if you don't pair it with a grinder that cost a lot more than the press ;)

Of course if you were using pre-ground coffee then yeah, that's gonna be super-bitter, because pre-ground is ground near-as-dammit for espress, moka pot or drip. French press needs VERY big, coarse - but evenly sized - grinds. That's actually hard to do. Any cheap grinder should be able to be reasonably consistent at the smaller sizes, but grinding large AND consistent is much tougher! For a moka pot or something you can use pre-ground or a $40 grinder, but for French press it's best with a $400 grinder.

And that's when you go "Holy shit; I didn't know coffee tasted like this!" - and fall deeper and deeper into the rabbit hole....