It is but it is the wrong way of pronouncing. Most Israelis don't know the difference between aleph and ayin, teth and tav, heth and khaf...don't know to pronounce ssode. I guess that is because of the Ashkenazi influence. In Syriac we have the same letters and each letter has a distinct sound. Also like the Yemenites pronounce, the gimel with a dagesh is a jimel!! That's sad most people don't follow the real pronounciation, but we can practice the real deal
There is no right and wrong pronunciation. The way letters are spoken varies over time and over space.
The Bible has the story of the shibboleth. That's where one clan was pronouncing the "sh" sound like an s. The Talmud complains about the residents of three cities who pronounce ayin as aleph and kheth as khaf.
Most of the differences you site have nothing to do with Ashkenazi influence. Only Yemenites pronounced all of those. The Jews of the Maghreb and of Iraq had their ayin and Kheth. All the other differences were missing there as well. You're implying that there is some pristine Hebrew that was pronounced correctly that the Yemenites preserve. It's just as likely that the Yemenites, being more isolated from the rest of the Jews, received much more influence from their Arab neighbors than did the people in the Maghreb.
The common accent in Israel these days is mostly the Sephardi rhythm, with its heavy use of Milra (accentuating the last syllable) but without the throaty consonants. Even most people with Maghreb roots have lost them by now. Some people with Yemenite roots still pronounce them, but that's fading as well. It's the way things go with living languages.
Again, the people of Benyamin's incapability to pronounce it (shibboleth) rightly is shown there. There is also a place where the sages have seen a person who can't differentiate aleph and ayin unfit for reciting a blessing. I am a Chaldean we have the same alphabet (again because of our Assyrian Jewish roots), we pronounce it that way too. You can see how much importance the pronunciation is given in the teachings of Rabbi David Bar Hayyim.
Not being able to pronounce rightly have always been associated with unlearned men. No two letters can sound the same/ be a combination of sounds in Hebrew, it is a standard rule kept by the sages long ago!!