Only people who live on social media believe these extreme views to be true. Most muslims hardly even know the difference or care.
Every single muslim, whether devout, practicing, lapsed or whatever, knows whether they are/were Sunni or Shia. They are literally born into it. It determines who is seen as the authority in matters of their faith, the way they pray, the sites they consider holy, the religious days they observe. Even Ramadan starts and ends on different days depending on which you are.
It's such a fundamental thing that I question whether you have any idea about what you're saying here.
It's like if you didn't know a single thing about Mandarin but insisted on making claims about its grammatical rules because you know English grammar.