Gaon:
I don’t think anybody denies that what you’re saying is true. Ideally, everyone would pronounce it correctly. The Mishnah Berurah does say in hilchos nasias kapayim that when a whole locality loses the ability the differentiate, they are still yotzei everything. He mentions that Russian Jews at his time did not differentiate between sin and shin.
Now allow me to say something that will inevitably make a lot of posters here freak out: sometimes it’s better to be normal than to be right.