So if a person who follows the Quran is not a Muslim who can say they are Muslim?

Then honestly how do you pray then? I'm not trying to hit back at you I completely respect you following the Qur'an and feeling as though it's the only correct book. But, many things weren't through just the Qur'an, many interpretations were from Prophet Mohammed's examples and words. At the end of the day, the Qur'an can have millions of interpretations however Prophet Mohammed was created to guide us through the most accurate interpretations that Allah swt wants. He taught us through the Qur'an, showed as manners, showed us how to react to different situations. He spread the Dawa' through not just the book, but through his actions too.