Being happy is the usual argument
To answer your question we need only consult the Qur'an. Messengers were sent as warners and for no other reason (16:35) (they will serve as a witness later). These warners could not guide us beyond the Message:
"Surely you cannot guide whom you love, but Allah guides whom He pleases, and He knows best the followers of the right way. And they say: If we follow the guidance with you, we shall be carried off from our country. What! have We not settled them in a safe, sacred territory to which fruits of every kind shall be drawn?-- a sustenance from Us; but most of them do not know."
Qur'an 28:56-57
So already it is established that following the Messenger means following the guidance with them.
The Qur’an is the truth (2:40-42, 2:91, 2:119, 2:147, 2:176, 5:48, 16:102). See 10:32-33 and the notes. The Qur’an is the sole guidance (2:63, 2:91, 2:176, 6:19, 6:114-115, 6:157, 7:144-147, 7:169-171, 12:111, 18:27, 21:45, 39:23, 45:6 etc.). Therefore those who introduce new sources of religious law are innovating and diverting Islam. All sects are forbidden and unnecessary.
The evidence is simply overwhelming. You can justify following a method of prayer (except praying silently at times and mentioning Muhammad (SAW)) but my point is upholding things which add nothing to the Message beyond embellishment (e.g. do you accept that a woman passing in front of a praying person nullifies their prayer?)
“And certainly Haroun had said to them before: O my people! you are only tried by it, and surely your Lord is the Beneficent Allah, therefore follow me and obey my order.”
Qur'an 20:90
Obeying the Messengers means obeying their judgements which will be according to the Message and following the guidance which they (the Messengers) themselves have received. In this instance people are to obey the Messengers by not associating others with Allah (SWT) (i.e. by following the Message). See also 20:92-93. Was Haroun another source of obligatory religious law besides Musa (SAW)??
“And had We destroyed them with chastisement before this, they would certainly have said: O our Lord! why didst Thou not send to us a messenger, for then we should have followed Thy communications before that we met disgrace and shame.”
20:134
Ah, so obeying the command requires following the Messengers (4:80) because Messengers brought the Message.
“And We do not send messengers but as givers of good news and warning, and those who disbelieve make a false contention that they may render null thereby the truth, and they take My communications and that with which they are warned for a mockery.”
18:56
Messengers are only warners. Disbelievers contend this ordinance.
“Say: I am only a mortal like you; it is revealed to me that your god is one Allah, therefore whoever hopes to meet his Lord, he should do good deeds, and not join any one in the service of his Lord.”
18:110
Muhammad (SAW) is not be worshipped nor held in regard (to religious teaching) as anything more than a Messenger and warner (6:19, 7:184, 7:203, 16:35). He adhered to and judged only by the Qur’an (5:48).
Do you see why "Qur'an-Alone" means the Qur'an?
“We know best what they listen to when they listen to you, and when they take counsel secretly, when the unjust say: You follow only a man deprived of reason.”
47
This ayah reveals that following the Messenger was following the Message that he delivered (see 10:2, 10:76, 21:3-5 etc.).
Remember that Messengers cannot guide. So how are we guided?
“Surely this Qur’an guides to that which is most upright and gives good news to the believers who do good that they shall have a great reward.”
17:9
remember accepting one single hadith which is false is hypocrisy
“Who isthen more unjust than who forges a lie against Allah or (who) gives the lie to His communications? Surely the guilty shall not be successful.”
17
So no-one should hold obligatory anything that is not in the Qur'an. We may consider ahadith as examples some of which are true, false good or bad, but it is quite impossible to refute the Qur'an and maintain a rival doctrine called "the Sunna". No doubt a lot of the sunna is ok, but it is not actually a sunna and is an example.
This way there will be no more deaths for apostasy or honour killings etc. etc. etc. And there will be no more arrogance from people.
I can quite more and more verses.
Peace.