Articles: [The] burial rites of [the] ancient Egiptians were very complex.

ReegisIs this sentence correct? Especially when it comes to the articles?

Not quite.

The burial rites of the ancient Egyptians were very complex.

Could you please explain why we should put the before burial rites and before ancient Egyptians?

Because you are speaking of specific rites (burial), and specific people (ancient Egyptians).

As far as I know, the fact that something is specific is not a sufficient condition to put the before it.

Here http://www.grammar-quizzes.com/article1a.html, it is explained this way:
A —SPECIFIC
In this example, the article a marks a noun as specific. It expresses a parti

The burial rites of the ancient Egyptians were very complex.

You cannot use "a" before plural nouns.

Yes, and of course I didn't mean this, I only wanted to say that specificity is not a sufficient condition to use a definite article.
But now I understand that since we cannot use an indefinite article, then we have a choice of whether to use a definite article or a zero article, and here specificity applies and settles the matter.

I think it depends on the fact that the Egyptians is a noun of nationality, like the French and so on.

But in my experience I have seen Italians, Americans without the many times.