>. For example, a knight didn't serve a lady in medieval literature -- he served the god.

Uhm, 50/50. Bear in mind Don Quixote made fun on the old farts from the Middle Ages saving "damisels" in distress. Sancho Panza was the simple, new man but far more grounded than Alonso Quijano which could be depicted as the last living "priest" because since 1492 no one gave a shit about kingdoms, local lords or whatever; everyone wanted to go to The Americas for a quick fortune (either by selling goods, or getting many more times food than in Spain).

>So, storytellers invented the adventure genre.

The adventure genre was what people liked before the mentioned Don Quixote, not by reading, but from folk tales, which are older than dirt, especially if you lived by the coast and met sailors around.

>this story becomes unconvincing too. Big villains and monsters are unimaginable,

Cosmic fears replaced big, concrete monsters (the rapist from the woods) with abstract fears under Lovecraft.

Nietzche depicted the old pre-Industrial values as obsolete. Lovecraft was scared of the new times. Cervantes just made a good laugh on both the "mythical, glorious times" but also on the "dumb, clueless future man". In the end both idealistic/realist roles learnt from each other across the adventure, which is what happens IRL in societies.

Cervantes was wiser, the laughted at the old fart seeing dangers everywhere against its outdated values, but so did on the new man with no "elevated" purposes.