If you want anime protagonists who aren’t heroic, maybe look into Evangelion, Chainsaw Man, or Fate Zero. They all subvert or dissect the hero archetype.

It's got 4 critic reviews - 2 positive and 2 negative. It apparently has 5000+ user ratings, but only 1 review, in which the reviewer praises it.

So I'm inclined to think the 0% audience score is a glitch, or the result of a bot mass-voting campaign or something.

I don't like how so many anime fans treat source material as sacred. If you want to see the most faithful version of "Trigun" possible, just read the manga.

This is clearly not a faithful retelling. It is using the characters, setting, and themes to tell a unique story. A "remix", effectively. Isn't that way more interesting than just a straight-up panel-to-screen conversion? Doesn't this give us the opportunity to be surprised, or to explore new ideas?