There's a stele that was discovered in 1986 [1] in Veracruz. You could be forgiven if you think that writing is Maya. But it is not. It some other language. A couple other small fragments like it have been found, but the stele is basically an hapax. It is the only example.
And from the one example, we can see that it a system overflowingly glorious in its maturity and complexity. The scribes belonged to a culture that had been writing for a very long time. That is the refinement of millennia.
There are dates carved on La Mojorra 1; if they are in the same Long Count calendar the Maya used, then the stele appears to be talking about something that happened in the 140s and 150s AD.
The obvious relationship between the Mesoamerican writing systems might be somewhat analogous to the Cyrillic and Latin alphabets, or Chinese and Japanese writing. One was adapted to write the other. Or they both evolved out of a common ancestral system. How far back might that have been?
[1] https://commons.wikimedia.org/wiki/File:La_Mojarra_Stela_1_S...
In middle egyptian (the language you probably assume) "pictures" are just syllables. They are phonetic, not semantic, in the same way letter of modern language correspond to sounds, not meanings.
Egyptians had no problem expressinyg conplex concepts and they also had cursive writing, which is much easier to write.
How can you tell that a script is "refined", especially from a single example?
"Has been shockingly overlooked by all but a handful of scholars since its discovery 125 years ago" -- really? I picked up the one popular book on the subject that I own. It was first published almost 25 years ago and has an entire chapter on proto-Elamite, plus about a dozen mentions throughout the book.
Everything seems to have some sort of fake narrative these days to make it more "interesting". <old-man-yells-at-cloud/>
P.S. Highly recommend the book: https://www.thamesandhudson.com/products/lost-languages