Games

I think that the devs don't intend for people to look everything up. The watchtower in the desert hints at players to try going up and finding the islands, which is a pretty direct hint that wouldn't be necessary if you were already the kind of freak who was gonna go up to the Sky Work to get some spells (granted, experienced players always prefer Hell over the Sky because there's fewer ways to get poly'd in Hell). You can find most of the bosses just moving to the sides from the main path, although you have to be very careful and know how to deal with swappers if you go for the Master of Masters through the intended path. The bosses you'd probably never find normally are Tiny, Meat Realm Kolmi, Mecha Kolmi (three you could find normally if you randomly stumble upon the overgrown cavern and keep exploring), the friend boss, the Leviathan (you could find him accidentally too if you're like me and dig into PWs super low just to avoid being on the surface where the hollow squidwards are, if you're coming back from E1 through the bottom for some reason), and the Forgotten, who is difficult to find even on purpose with noitamap.com in my second screen.

Main reason you wouldn't find those organically is because runs that get far enough that you have the possibility of finding them make most players risk-averse enough to look them up first.