The Qur’an is meant to be read and understood holistically, which is why it’s a concise book - there are only so many verses in the Qur’an what seems like repetition might be considered wasteful, but it’s not repetition - it’s the Qur’an explaining itself from various vantage points (6:65).
There are no contradictions in the Qur’an (4:82). If there are verses that seem to contradict each other, then we must revise our understanding of the verses, not discard then through some fake doctrine of abrogation. The Qur’an is perfected.
Verses do not cancel each other out. They must all hold true at all times.
Use your reasoning and intellect (2:44, 2:76, 3:65, 6:32, 7:169, 10:16, 11:51, 12:109, 23:80, 37:138…) God really, really wants you to use your brain.
The Qur’an says it is complete guidance (6:38, 6:114, 7:52, 11:1, 12:111). Again, the repetition is significant.
Do not seek religious guidance outside of revelation (7:185, 9:31, 39:23, 45:6, 68:36-38, 77:50). Again the point is repeated for stress.
Do not mix truth and falsehood (2:42). if you have a book that is partly true and partly false, ditch the book altogether. This is simply common sense, if you think of it, but God felt it needed to be said.
Do not ask for unnecessary details (5:101) - use your intellect and do what God asks of you. Children know this, asking for details of things they don’t really want to do, but have to.
The messenger’s role is as a warner and conveyor of revelation - this is repeated in many many verses - 2:119, 7:184, 7:188, 11:2, 11:12, 17:105, 22:49 and numerous others.
Prophet Muhammad was not allowed to change God’s laws - in 66:1 he was chastised for prohibiting something for himself that was not prohibited by God, much less add new ones (16:116 “do not keep uttering in falsehood, "This is lawful and this is unlawful”, thus inventing lies against God”)
Verify everything for yourself by using your senses and intellect (17:36).
And then it says “Obey God and obey the Messenger” (4:59, 5:92, 24:54, 24:56, 47:33, 64:12) and that the messenger of God is a most excellent example (33:21).
In light of the above principles of the Qur’an, we can only conclude that obeying the Messenger means only what the Messenger relayed as revelation, in the complete book of guidance. No other text is allowed.
45:6 These are the verses of God We convey to you with truth. Then, in what HADITH, if not in God and His verses, will they believe?
To claim that the hadith is required for the practice of Islam introduces contradictions in the above #3, #4, and #6. That not all the hadith is true, and yet is to be considered as a source of religion next to the Qur’an flouts #5.
Other considerations
There is a great tendency to conflate terms used in the Qur'an and think of them as one and the same. In this case "Prophet" and "Messenger" - true, they are the same person, but the roles and responsibilities are not the same, and God uses these words very precisely in the Qur'an. In the Messenger role, Muhammad does not speak from his own desire - he only conveys God's words. In the Prophet's role, he is a fallible human being, with human foibles and needs. And in the Qur'an God chastises the Prophet after he has made mistakes - turning away the blind (80:1-2), or prohibiting something that God did not (66:1) In fact, it is very pertinent that God addresses the Prophet and not the Messenger in 66:1 - clearly telling us that the Prophet cannot change God's Laws. This repeats the injunction in 16:116 - do not keep uttering in falsehood, "This is lawful and this is unlawful”, thus inventing lies against God. Those who fabricate lies against God, fail to prosper in their own ‘self’. Thus the Qur'an always states “Obey Me and obey the messenger” and never “Obey Me and obey the prophet”
“Obey Me and obey the messenger” is not unique to Prophet Muhammad - it is mentioned for Prophets Noah (26:108, 71:3), Hud (26:126), Saaleh (26:144., 26:150), Lot (26:163), and Shu’aib (26:179). Now if obeying the messenger meant following the messenger's sunnah, then to obey God properly, one must look for the sunnah of these other messengers as well, because we cannot pick and choose which verses we want to follow, right? We cannot say "we want to obey the Qur'an only when the messenger refers to Muhammad" and when it isn't Muhammad, we are going to ignore those verses. Thus obeying the messenger is limited to what the messenger brings, i.e. God's message.
The people who lived around Prophet Muhammad were told to be punctual if they were invited for a meal and to leave immediately afterwards and not hang around waiting for hadith (33:53 actually uses the word hadith)
In verses 2:136 and 2:285, people who believe in the prophets and make no distinction between them are considered Muslims by God
Similarly, in 22:78, the people who believe in the creed of Abraham, God has named Muslimeen in the bygone days (in prior revelations) and in the Qur’an. In God’s eyes, there is no requirement for anything other than belief in the revelations for being considered Muslim, no hadith of Abraham, hadith of Moses, hadith of Jesus, or hadith of Muhammad, which at the time this verse was revealed, had yet to exist.
Verse 53:3 is often quoted to say that the Prophet doesn’t speak on his own, to imply that everything that comes out of his mouth is revelation. But the next verse 53:4 clarifies - the Qur’an is but a revelation that is being revealed. The Prophet does have a life and speaks of things other than revelation, but we are not to take those as revelation. This understanding that everything he says is revelation also contradicts with 33:53 (“if you are invited to dinner, do not hang around waiting for hadith”)
Who selected the hadith? Not allegedly said or did what's in the hadith but who selected them? The answer is the collector whose name is on the collection like Bukhari! Bukhari allegedly travelled wherever and spoke to whomever and judged the chain of names of people he never met to be 'sound'. That is how a hadith comes us. So who are you really obeying? Not the messenger but Bukhari, or Muslim, or Tarmidhi. (c.f Farouk A Peru)
In conclusion, Islam is only in the revelations from God (22:78).