Anarcho-primitives would disagree with you, and would have their choice anthropological case studies of hunter-gatherer or pastoral tribal peoples who seemingly live without hierarchy. On the other end of the spectrum, there's Roddenberry utopian sci-fi visions of the disappearance of hierarchies- at least those organized around property- in post-scarcity worlds. And even in tech, there are modern day utopians who try to build "holacracy" and flat organizations, always with decidedly mixed-to-negative results.

I'm not endorsing this argument one way or another, just saying that hierarchies as they exist now are not inevitable, and the act of presuming that there is no alternative is an act of lack of imagination.

Keep in mind "no hierarchies" in these cultural studies does not mean that there are no authority figures or that there aren't any leaders. In many situation it is more practical to have one decision maker rather than always deferring to a democratic discussion.

But the key difference is that the authority granted to these leaders is conditional and temporary. If the group loses their faith in the leader or the leader is no longer absolutely necessary, they can fall back to the democratic process again.

Likewise in federal communal structures an individual commune or neighborhood can always object and, if its members don't feel adequately represented, secede without threats of violence.

We recognise this level of autonomy in super-national structures like the European Union (hence the discussions around "Brexit" and such), yet we seem to treat them as unthinkable within a nation and any mention of autonomy at the communal level is easily seen as absurd. This is because nationhood has become our widespread cultural norm to the point we can rarely even entertain the notion of an alternative or a time before or after nation states.

The problem with the word "hierarchy" is that most people conflate very different concepts when talking about whether it is or isn't necessary.

Anarchism doesn't say there should be nobody in charge, just that authority should be as limited as possible and only seen as temporary and conditional.

Nation states centralise power. Even supposedly democratic nation states routinely follow policies the majority of their citizens disagrees with. Even disregarding the problems with first-past-the-post election systems, individual voters or even voter blocks have hardly any way to have their views represented or hold their representatives immediately accountable.

Capitalism exacerbates this problem because it consolidates wealth and at scale (think billionaires, not millionaires) that wealth is equivalent to political power, allowing individuals and corporations to control politicians and thus policy, both by directly influencing individual politicians and by influencing public opinion to place "their" politicians in positions of power.

Democratic Confederalism for instance embraces a communalist "free association" model of autonomous neighborhoods collaborating as communities and so on. Ultimately you still end up with federal super-structures but all power rests at the base rather than the top.

The usual counter argument is "that is nice, but this can never work in practice" or "this can't scale" but in practice it does. Look into the Mondragon Corporation (a coop of currently ~75k workers) or the political structure of the Autonomous Administration of North East Syria (Rojava).

Another typical argument is that they don't look very different from the outside or are practically identical with the current systems if you squint really hard and tilt your head sideways: that is intentional. The differences become apparent when there are conflicts of interest or other times of crisis.