"Fascism" is admittedly a very fickle word, so if you ask me what I think it means: it's not simply authoritarianism, nor is it simply believing that the past was better, it's cargo cult authoritarianism based not on arbitrary nostalgia but naive holism.
Specifically, it's based on the idea that prior to certain developments, there was a holistic system that was inherently composed and self-regulating in a way that was not simply modified or made worse later developments but outright ruptured.
This is not the same thing as Chesterton's Fence. A programmer may avoid touching some extremely old code even if they think it's bad in order to avoid unintended consequences, but you don't see them insisting the old code is some perfect computational harmony.
If you understand that just because changing something works on paper doesn't necessarily mean it's a good idea to tamper with it, that's just wisdom. If you're especially conservative about tampering with such things that just makes you, well, conservative, not fascist.
Fascism, by contrast, is a modernized garden of eden narrative: there's a pseudo-historical idea of a harmony having existed that now does not exist. They might not claim it was paradise, but they'll insist it was fundamentally Natural.
Or to put it another way, there was a Spirit that was embodied by the specific composition of the alleged society of the past. The goal of fascism is to restore this Spirit, this specific form of collective consciousness, and in order to do this one must recreate the conditions.
Since the past was this alleged Whole, where everything played a part, it's imperative that everyone adopt exactly those practices, to not simply revert policy but to revert ritual, to revert aesthetics. This is what I mean about it being a cargo cult: it's LARPing all the way down.
And this also puts it in an interesting contrast with communism and why some fascist systems have either compared themselves to socialism or called themselves "socialist". With both fascism and communism, the idea of "collective consciousness" exists, but the goal of communism is to build a collective consciousness that never was, as a next evolutionary step. The goal of fascism is to restore a supposed collective consciousness that existed in the past. This isn't an endorsement of communism, but it does highlight a difference
For the record I don't identify as either pro or anti communism, and I really don't want to make this thread about that. My point here, to reiterate, is that fascism is aestheticized authoritarianism borne of a naive notion of a lost "whole" devoid of any caveats or contingency.
But just to be sure here, there's plenty of other kinds of authoritarianism that can be potentially just as bad. The opposite kind of authoritarianism is a kind of unhinged scientism, like the USSR's reckless embrace of Lysenkoism or Mao's "Four Pests" campaign.
But in both cases, a totalitarian government is a possible, arguably even "natural" step because that's the "interim" stage to get everyone to get with the program, and to defang or eliminate those who may potentially sabotage the project of creating or restoring the voice of the collective.
With all that being said, there are things that work as wholes: organisms and systems alike co-evolve to fit each other like pieces of a puzzle, and taking that for granted can lead to dangerous hubris, but if you start to fetishize such "wholeness" as inherently optimal that's also hubris. Co-evolution is a process, and in the midst of it there's all kinds of volatility, inefficiency, outright waste, local optima that can become a liability down the road, and just tons of suffering. There's no easy answer to dealing with any of that, but cargo-culting isn't it.