Great example.
But... IDK if this (or other clearly advanced writing systems) demonstrate "refinement of millennia."
I think we have a "history is accelerating" bias. Changes in the deep past happened slowly, and the pace of change increases over time. That may be true from a very broad POV... but I don't think it's true on shorter timescales.
There are no hard limitations on going from a newly invented writing system to a professional scribal culture in a single generation. I don't think watershed "revolutions" are something new. Egyptian writing, and Early bronze age egyptian culture more broadly gets very advanced, very quickly. We don't really know what elements have deep histories... but it's hard to explain ancient egypt without allowing for some impressive leaps. Hence aliens.
Also... "common ancestor" can be a lot of things. It could be like the gradual species-like philogenetics of cyrillic, latin, hebrew, arabic and all other alphabets' development from proto-sinaitic and canaanite/punic. The same script gradually evolving in different scriptural islands.
Otoh... "ancestry" can be pure inspiration. The idea of writing, its uses and the certainty that widespread literacy is possible can be the "dna."
The confusing part is that culture does, often, evolve very gradually like species and clades over time. These sometimes leave evidence of the whole process. Sudden explosions can't be deduced from the absence of evidence.
Mythology is involved in inhibiting invention. I mean, after inventing invention, the concept of it, you have a certain motivation, which is lacking in a culture that tells stories about how its greatest inventions were stolen from the gods by fantasy heroes. We still indulge in those stories slightly, by mythologizing inventors. But at least we don't have a cyclical concept of time where everything's predestined by the fates, and we all have proper roles and places, and there's no progress except round and round. That's a tranquil outlook, but tends to be self-fulfilling.
I agree. It's just hard to say anything with certainty (or even clarity) about these "mentality" components. A culture's mythology. It's "concept of concepts." It's so vague and abstract that we can't even name it legibly.