One way ideology expresses itself in fiction is that narratives are set up to justify whatever actions the creator ideologically supports. The creator has full control over the world they're creating, so the very act of setting up a scenario that justifies genocide or torture or murder is ideology. Home Alone is another example, basically a suburbanite violence fantasy about torturing and maiming the Other, but the way it's written the violent acts are justified because the Other "deserved it". But the whole idea of the Other deserving it is an assumption baked into white suburbanite ideology.

All that being said, (and having not read the manga, and the anime isn't finished yet last I checked so idk) AoT the anime doesn't have to be read as endorsing fascism yet imo. Rather it has portrayals of fascist influences and motivations in various characters and factions. The show illustrates how strongly narratives and symbols tie into fascism, how mythology can bring people together to willingly go along with terrible crimes. A recurring theme is how every faction claims they're "trying to save humanity" while committing mass murder, with ever increasing stakes and consequences. It shows fascist justifications and mythology taken to their logical conclusion. I'm hoping the ending doesn't force a fascist-friendly interpretation.

And sometimes I'm in the mood for some edgy, violent, dramatic slop that reminds me of my childhood. edit: as in a show I watched as a teen, not I had to kill titans as a child lmao