How is it possible for a human to beat a servant?

Just finished the VN.
Wasn't it established day one in Fate/Zero that a humans can't stand up to servants?

That's a sword

Nasu is a hack.

FSN predates Zero you fucking retard.

Nasu creates rules for the sole purpose of breaking them

You know that most "servants" are humans to begin with right? Shiro litterally cheats by getting the strengh of his future self that became a hero.

E rank stats are only like 10 times a normal human without magic.

Saber survived while Shirou became a vegetable, so she won. And Saber was going easy on Shirou since she didn't think he could threaten her. She was complacent and paid for it.

Why does Nasu like to pretend that Archer is a "mediocre" servant?
Yet he's able to project any NP to counter any servant plus he's able to nuke people with broken NPs.

He still won the fight though, Seibah herself said so.