Why do Islamic sects diverge, when they have Allah's Book to judge between them? Is my not belonging to any sect except Islam a mistake, knowing that I only seek evidence from the Quran?

Everything that requires intellectual exertion or profound understanding should not be attributed to those who are not qualified and proficient, especially discourse concerning the religion of Allah and the rulings of His Shari'ah. It is not permissible to delve into it without knowledge, nor is it proper to consult anyone other than the scholars, the inheritors of the prophets, regarding it. If anyone other than scholars speaks about religion, clear misguidance occurs. Thus, matters of knowledge and issues of Shari'ah should not be discussed by those who are not knowledgeable.

As for disagreement among people, it is unavoidable, and fortunate is he who takes an argument that will benefit him before Allah. This can only be achieved by holding fast to the Book of Allah and the Sunnah of His Messenger, and by following those whom Allah and His Messenger have purified, from among the Companions and their followers. As for His Almighty saying: "Indeed, those who divided their religion and became sects - you are not [associated] with them in anything," this verse is general for anyone who deviates from the religion of Allah, whose law is one and without disagreement. So, whoever differs in it and becomes sects, Allah has absolved His Messenger from what they are involved in.

As for not affiliating with the Sunni madhhab, while adhering to the name of Islam, this is acceptable when people agree on the meaning of Islam, and there is no need for other titles. However, if people differ on the meaning of Islam and each group adheres to its own understanding, then it is not enough for a person at that time to merely identify with Islam. When a group deviates and disparages the fundamentals of religion, a person cannot but disassociate himself from them.

As for the questioner's request not to use anything but the Quran for evidence, this is a mistake, for the Sunnah is essential for understanding the Quran and implementing its rulings. Allah has preserved the Sunnah of His Prophet just as He preserved His Book, and the preserved Sunnah cannot contradict the Quran. The people of knowledge clarify what is ambiguous and explain its objectives.