The complexity of the Holy Quran is one of God's miracles . God doesn't repeat things in the Quran ''to fill the empty gaps". God repeats things for many reasons; one of them is for emphasis. You may ask why God had inspired such a complicated scripture to prophet Muhammad (PBUH). The answer to this question can be summed up in just two points:-
1- Prophet Muhammad (PBUH) was illiterate and couldn't read or write. He was dictating the Quran to his educated companions . So how can an illiterate person invent and come up with such a complicated divine book???
2- If you learned Arabic and read the Quran, you would find it so difficult to write something as fluent as it and even understand it, that would make the Islamic scholars compete to interpret, study and keep it; which would keep the Quran one way or another from distortion and oblivion. If anybody wanted to be fluent in Arabic, he should study God's unmistakable Holy Scripture the Quran (i.e Quran is the main source of Arabic rhetoric, syntax and grammar till now). Pagan Arabs in the time of the prophet accused him of sorcery because of God's revelation to him. They said that those verses were so sweet and touching that they couldn't be written by a human. Being them pagans who didn't believe in One God and rather believed in occultism, they said that prophet Muhammad was a sorcerer and whose book was ''a group of magical spells inspired to him by demons in order to bewitch people and convince them to embrace Islam" .
Hope you are convinced Peace be upon you!!
Hmm... Well I am not convinced that the Quran as a work is in itself miraculous. However, I will accept that to the 6th century Pagans of Arabia it would have seemed so.
Blessing. C