Term for ultimately pointless effort [closed]

Futile [fyoot-l, fyoo-tahyl] adjective 1. incapable of producing any result; ineffective; useless; not successful: Attempting to force-feed the sick horse was futile. 2. trifling; frivolous; unimportant.

Classically speaking this would be Sisyphean.

In Greek mythology Sisyphus was the king of Ephyra (now known as Corinth). He was punished for his self-aggrandizing craftiness and deceitfulness by being forced to roll an immense boulder up a hill, only to watch it come back to hit him, repeating this action for eternity. Through the classical influence on modern culture, tasks that are both laborious and futile are therefore described as Sisyphean.

Depending on the actual amount of effort involved in the writing process I may be on a bit of a hyperbole, though. For you to judge.

Reference:
https://en.wikipedia.org/wiki/Sisyphus

(In) vain should work.

"Well, that was a vain effort".
"Well, that effort was in vain".

M-W:

vain adjective
2:  marked by futility or ineffectualness :  unsuccessful,useless : vain efforts to escape

- in vain

1:  to no end :  without success or result : her efforts were in vain

A vain effort to quell the public's fears only made matters worse.

Volunteers searched the area in the vain hope of finding clues.