You are likely not paying attention to those things and are essentially speed running the games. There is a lot of narrative build up to Gwyn, Lorian & Lothric (although they are the penultimate boss), and a final fight with Genichiro (which turns into a fight with Isshin). And while less expected, Old King Allant, Soul of Cinder, Gehrman/The Moon Presence, and to a lesser extent, Nashandra/Aldia still make narrative sense in retrospect -- if you have been paying attention.

None of them are "just there." If that is the conclusion you came to then you either aren't paying attention, put little though into understanding it, or you did those things and it simply went over your head regardless. I get the impression that English is not your first language -- maybe some of the nuance was lost on you?