Why this game is so unclean?

I finished this game a few hours ago and I realized i don't met with some side bosses and places,there was no sign to even know about this.Game is so single-line and without souls Wiki and YouTube i would not play this game that long. I avoided spoilers but I had no idea where to go after.I finished this game by beating The Soul of Cinder and Gael Knight in Ringed city.I heard about this problem by other non souls players but this is terrible for me.Bloodborn also had this same issue....no hate