All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
Many people in Arab countries have changed the pronunciation of some words in the Arabic language, to an extent that some countries have their own dialect. But the rules of the Arabic language did not change over time, and the Quran was not affected by what happened because the reciters of the Quran recite it orally from one person to another, and they are keen on preserving its correct articulations and its different modes of recitations.
Al-Jazari wrote in Munjid Al-Muqri’een wa Murshid At-Taalibeen:
"The science of Qiraa'aat is the discipline that studies the recitation (pronunciation) of the words of the Quran and their differences, from one reciter to another who heard it orally ... and the reciter is the one who knows its pronunciation and who heard it orally; for example, if a reciter had learned the book entitled ‘At-Tayseer fi Al-Qiraa’aat As-Sab’ (which is a book about the seven modes of the recitation of the Quran), then he is not entitled to teach what is in it unless he had heard it orally from someone who had heard it orally from another, and so forth, because there are things in the recitations that could not be recited properly except by hearing it and orally saying it."
Allaah knows best.