I would add that a substantial part of the problem is the argument for why it is supposed to be so important to cut and distribute power.
Depending on the time, the subtleties of what passes for political theory in the 21st century can be ignored, dismissed as naive nonsense, or outright considered inapplicable.
People accustomed to a political theory limited to "the king is king because God put him there" are not likely to understand or care about nonsensical discourses about nebulous concepts like "checks and balances", "separation of powers" or to consider downright criminal the idea that the three branches of the government dedicate themselves to "check" and sabotage each other instead of working together.
While I'm unsure I'd go quite that far, I do more or less agree with the point; regardless of SI or not, unless a society was already becoming democratic or had strong democratic leanings, its going to be more than an uphill climb to do more than make some motions in that direction cos its so out of context and lived experience.
Its like trying to jump to steel from copper, both are metals that can be used and shaped amazingly, but they function so radically differently that someone hos only experience is copper is going to more than struggle with steel and politics is infinitely more messy and complicated and confusing than shaping metal.
Hell, let's take a historical "democracy" Ancient Athens; if a person or SI tried to say, ensure Athenian women could vote, they'd likely be eaten alive given the violently misogynistic culture.
To quote John Gould:
The juridical status of women in Athens is beautifully indicated by the single entry under "women" in the index to Harrison's
Law of Athens i: it reads simply "women, disabilities". — John Gould, "Law, Custom and Myth: Aspects of the Social Position of Women in Classical Athens
Now, obviously women in Athens would probably like a vote (On average at least) in the same and even greater vein to how slaves sure as hell didn't want to be slaves; but if you're going to overturn those societal conventions then even in a "democracy" you're in for a bad time. It'd be a good thing to try, I'd definitely support it, but under such circumstances you'd be lucky to not end up with a civil war, or mass killings, or any number of horrible events in a bid to stop it, if the idea even kind of got off the ground. If one doesn't mind breaking and remaking society, that's fine, but its not exactly an easy process and there's massive chances for total failure or ideas being rolled back ETC.
Essentially, societal inertia, traditional cultures and beliefs, those in power, structures and systems, all those things at a minimum are in the way of massive societal and structural changes but also serve as the basis for how a culture develops and changes. Radical paradigm shifts are extremely rare to near none existent without being built up to: IE Rome's Republic didn't actually change much as most of the Republic systems were already in place, they didn't create it whole cloth, it was already there, they just re-shuffled things a bit by removing the king.
In this context, a historical figure or SI is liable to be stuck with one or two options for radically altering the political landscape. Either A, nudging the nation towards a path they would want, or B, burning the entire damn system down and rebuilding it from scratch, or sub-section -B running away with one's supporters to try the idea elsewhere if there is anywhere to go.