Namely, you learned that "an Assembly composed of all citizens" is not meaningful democracy if the class of "citizens" is defined so narrowly that this comes out to a tiny ruling class dominating a vast majority of subjugated people.

That is a good description of the Athenian democracy where only landed indigenous men were part of the demos, women had no rights, let alone the right to vote, immigrants (metoikoi) also could not vote or own real estate and the economy was supported by relentless slave labour.

Note, all this was 2,000 years ago.

It's fascist, but still a democracy of sorts. Of course, the fact that it is fascist means it shouldn't be worshipped.

Not desiring Fascism through Democracy is one of the reasons the US has a bicameral legislature and the President has a veto power. Much of the Federal Structure is to protect the rights of the individual in the context of rulemaking by the majority. This is a constant source of friction, but it is intentional, the reasons for which are shown in this very discussion.