The problem some people have is with the lack of the word "other". The argument goes likes this:
If you are talking about Egypt as a country today and you want to compare it to the religious beliefs of ancient civilizations, you would say "than any ancient civilization" - because Egypt in this sentance is not an ancient civilization. And if you want to say the size of a comet in space is larger "than New York City", that's fine, because you aren't saying or implying the comet is a city in the United States.
The problem comes in when you are comparing two things that are in the same class. So if I were to say, "Usain Bolt is faster than any human!" some aggrieved soul might respond, "Are you saying black people aren't human? Racist!" (And I would have the irresistible urge to tell such a person to go and self-stimulate themselves with a cactus.) By omitting the word "other" it is said that the sentence would imply Mr Bolt isn't human, you see.
So the 'problem' is that the bit "the Egyptians of ages past carried this idea further than any ancient civilization" is said to suggest the Egyptians spoken about here aren't actually an ancient civilization.
Do I find such an argument persuasive? Frankly, I think this borderlines on imbecilic pedantry on the order of "may I go to the bathroom vs can I go to the bathroom" and for all I know is a leading cause of death among English pedants (oh how I wish it were).
However, there are some who will claim that omitting the 'other' is wrong even when it is perfectly obvious what is meant in the sentence itself. It can be objectively wrong when it leads to confusion or definite ambiguity, and where using "other" in it's rightful place would solve the issue.
So that's what they are talking about. As a matter of pragmatism, I suggest you find out who such people are and do your best to stay away from the nattering nabobs of nitpicking.