Is it permissible for a Muslim not to be observant of the teachings of their religion?

A Muslim must adhere to obligations and avoid prohibitions. If a person abandons obligations or commits prohibitions, and the matter reaches the level of disbelief (kufr) and polytheism (shirk), such as deeming permissible what is known to be forbidden in Islam by necessity, then he is an apostate from Islam. However, if he commits sins that are not considered disbelief, he is subject to God's threat of painful torment and worldly punishments. The duty towards such individuals is to advise them and call them to repentance. The disobedient Muslim who possesses the essence of monotheism is better than the atheist disbeliever, despite his shortcomings, for monotheism is the greatest of good deeds.