That's how Unicode started but nowadays Unicode expresses things that are only used because Unicode itself introduced them.
And this while many important things in the "have used text in history" category have been unfinished or not tackled at all.
The way I see it, emojis are practically single-handedly responsible for near-universal adoption of Unicode in the Anglosphere. Otherwise, it would be all too easy for lazy developers to just use ASCII and then shove their fingers in their ears about any other writing systems.
My point is that Unicode's own mission statement says: "The Unicode Consortium enables people around the world to use computers in any language."
I think it strayed from that. And I'd argue the mission was only ever fulfilled when seen through an anglospheric lens. You don't even have to summon Han Unification, the elephant in the room. Documents from Western Europe from a couple of decades ago can't be represented properly.
Example: you cannot properly represent a German telephone book today. Take "Müller" and the French surname "Haüy". Both contain the same Unicode character, but in "Müller" it is an umlaut and sorts like "ue" (Mueller), while in "Haüy" it is a trema and sorts like a plain u (Hauy). For all intents and purposes these are different letters. That they look similar (not the same, in proper typography) is a mere coincidence. Yet Unicode encodes them identically, so the information needed to sort correctly is simply not in the text anymore.
Han Unification is the other sore point, and a much bigger one.
I'd like Unicode to focus on its core mission, encoding the languages that exist, before it starts shaping new ones. For that I'd propose a grace period: a new character should have to be in significant active use for 10 to 20 years (not merely implemented on a popular device) before it is accepted into the standard.