The Surah speaks for itself. Like I said I'm not taking the word of a human over the word of Allah swt.Your logic takes you outside of Islam. If prophet mohammed was like you and me, then we can both object to what he said in explaining Islam since he had no legal religious status like us. But since we both agree, and I am assuming you claim to be a muslim, that he is the messenger of Allah sent with the Quran and with equal authority through his teaching and explanation(Sunnah, authenticated by muslim consensus), Prophet mohamed is not like you or me and his word carries religious authority. His sayings are a must follow when it relates to the fundamentals of Islam.
The fact is, if you pray five times a day, the method you perform your prayer is directly from the prophet's teaching through his Hadeeths.
Saixb., if you want to have your own ways of performing acts of worship, then Islam is not for you. Islam is strictly religion with two sources: Quran and Sunnah. It is not allowed for anybody to add onto or take something out from it. This is what makes Islam different from other previous religions that were screwed up by their followers who took liberty at writing and changing their religions as they saw fit over the centuries.