I don't think that's true. Mesoamerica had a very rich tradition of papermaking (Amatl) that predated paper in Europe (though probably not Chinese). Colonists severely repressed, criminalized, and even destroyed the paper and writing systems. Thousands of Maya codices were burned in 1562. Almost all pre-colombian libraries (amoxcalli) were destroyed
We've deciphered Nahuatl and Maya script but Zapotec, Olmec, Isthmian, Quipu, and other scripts are still not well understood
The destruction during the Spanish conquests of the Aztecs and others was terrible. It was also rather disorganized initially, especially due to the huge delays regarding communication between the Americas and Europe.
In regards to paper, while the Aztecs had impressive achievements, especially considering the almost complete isolation of the Americas from the rest of the world (is there any civilization close to the achievements of the Aztecs and other Amerindians in Africa south of Egypt?), are you sure that amatl/amate counts as paper? It was possibly stretched bark, and not woven.
> The Maya used a writing material called huun starting from the 5th century. It was made from the inner bark of the wild fig tree. It was cut and stretched thin rather than made of randomly woven fibers, which according to one source, disqualified it as true paper.
The Mali Empire was not far south of Egypt, it overlapped with the Sahara and was relatively late, 1235-1610, and is primarily known for its rich natural resources, namely gold, which cannot be said to be an achievement. It was significantly large and did last for centuries, at least. It had lots of contact with others, such as regarding the empire more or less adhering to Islam. There are some mosques there, but some of them are adobe buildings, and some of them were reconstructed in the 1900s. Apart from gold, which is not an achievement, what achievements did the Mali empire have that comes close to that of the Aztecs and other Amerindians? Manding languages did not have their own script as far as I can tell, only Arabic and Latin.
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Great Zimbabwe's Great Enclosure is something, but it seems much less impressive than that of for instance Chichen Itza, despite being younger. And Great Zimbabwe must have had international trade, given artifacts from China was found there. On the other hand, archeologists and Europeans accidentally damaged it, and time wore it down, and thus it might have been more impressive than the current ruins indicate. The building approach with small, mortarless stones, and wooden lintel instead of arches or huge stones, despite the time period being 1100s to 1500s, might have limited what could be constructed, but perhaps the original edifices employed other techniques as well than wooden lintel. Though I do not understand how the wooden lintel survived that many centuries. Dry climate?
It more or less bordered or was really close to Egypt, and it was on the very coastal edge of the African continent, as close as is possible to the Arabian Peninsula, and even conquered territory outside Africa. And if the conquered parts are included, it was somewhat east as well at the very least. Did it only conquer in that direction? There are the Adwa mountains (and even the active stratovolcano Adwa), somewhat separating Axum from its south-western direction further into Africa. The capital Axum was at a very high elevation in the highlands, like more than 2000 meters above sea level, and relatively close to the other major cities. Deserts might also have separated stretches of the empire to its west. It also must have had a lot of foreign influence, as per the Greek writing on some of its coins. And the capital Axum itself was relatively close to the coast. And one description I found just mentioned coastal or near-coastal Axum cities, not cities much further inland. Adulis was coastal, and Matara like Axum was not far from the coast. I do not know if it had any other cities. One source mentions Ptolemais Theron as a coastal city.
And then some writers describe the Aksum empire as highly cosmopolitan, like Adulis having a large Greek population.
If it had partial natural borders like deserts, mountains and an active volcano, somewhat separating it from the rest of Africa in its south-western and western direction, and sizable numbers of Greeks and other peoples, and located on the very edge of Africa as close as possible to the Arabian Peninsula, it doesn't really seem to me to be the best example, upon closer examination. I can sort of understand why you would mention it as an example, though
We've deciphered Nahuatl and Maya script but Zapotec, Olmec, Isthmian, Quipu, and other scripts are still not well understood