Since the sound of the “Ayin” is absent from all Indo-European (a.k.a. Aryan) languages, virtually all Ashkenazim and many Sefardim will find it very difficult to pronounce it. The same goes (for English speakers) with the sounds associated with Aleph, Hes, Chaf and Heh.
Given the Hebrew has always been a living language (contrary to zionist propaganda that Hebrew died out millenia ago and was re-invented by Ben Yehudah & friends), the prononciation and grammar are constantly changing.