I have noticed little fundamental differences between Egyptian and other languages.
And where are you getting the idea that there's "almost no words" in the vocabulary? The TLA alone currently lists more than 55 000.
Ancient Language was translated and interpreted in terms of later language and especially the language and writing found in "the book of the dead". IT was merely assumed the earlier writing was written in the same language because these languages which aren't mutually intelligible share a vocabulary. Indeed, neither of these languages can even be translated into the other because formatting is different. Ancient Language translated into modern languages looks like gobbledty gook and any modern language translated into Ancient Language would just be a stream of disjointed words... more akin to random words than coherent thought or word soup.
While we still use the same vocabulary as Ancient Language all the words have evolved in every language such as "mother" which changes even within each language tens of thousands of words have needed to be added to achieve communication with our symbolic, analog, and abstract language. We each parse sentences uniquely which makes communication difficult so we add words to force a single interpretation which helps but ironically it increases the number of possible interpretations and assures none is exactly what the author intended. How many interpreted that last sentence exactly as I intended? Each reader believes he did and few will consider other interpretations are even possible. Ancient Language sentences each had only one single possible interpretation and every listener heard this or he heard nonsense so he knew he missed the meaning.
The is where and why the TLA is wrong. The authors assumed it was all one language so they tossed all the words into a dictionary with no regard to where or when the words were found or how they were used. They found 55,000 of them but never noticed there were fewer than 2000 represented in the Ancient Language.
If you don't believe it just open any dictionary to any page and count the number of words in it that appear in the Pyramid Texts. About 2% appear because Ancient Language had almost no words and most were nouns. The writing breaks Zipf's Law because the authors didn't think like we do. We think linearly and they thought four dimensionally. They didn't even experience thought and had no word that meant "thought" or implied they knew what thinking was! They were very different than every Egyptologist. This is all really quite obvious once you see it but we can't see it because we can't even imagine a metaphysical language or not experiencing thought. We are at arms length from our consciousness because we only experience thought.
All the fundamental differences are hidden by bad methodology which assumes there was no change and a 3000 year "cultural context" and by our inability to read the writing or translate it without thinking. Ancient wouldbe translators had the same problem with the additional problem that they lacked any kind of science whatsoever and Ancient Language was formatted in ancient science. It was their knowledge of reality that created the formatting for their communication just like honey bees or any other "animal". Ancient translators gave us alchemy, astrology, the Bible, Hermetic writings, etc etc. But they ran out of source material ~500 BC because papyrus doesn't hold up. Remember writing was invented to record modern languages to prevent drift in meaning so relatively little was ever even written in AL.