There are required bosses. You have to beat the main ones to beat the game you can't just run by em.
You can skip optional areas and optional bosses, but the main ones are not optional.
That being said yes I beat them all and platinumed the game and dlc.
Defiled Amygdala, Orphan of Kos
I shutter to think.
That fukking Fire Dog in the defiled chalice.too.
You will crack the code don't give up. Once you do you will likely want to play other Fromsoft games. These games seem harder than they are because of the preconceived notions they have. Just relax and use the mechanics to your advantage.
You can essentially roll and parry your way to victory just make good decisions.
These games are not nearly as hard as people think, you just have to get over that first hump.