The only religion which has remained in its pure and original form is the religion of Islam. No other religion enjoys this privilege as with the passage of time people began to make additions and omissions into their religion. They added into their religion things that had no basis whatsoever, and there was no one to weed them out of their wrongs. As a result it became difficult for them to differentiate between the original practices and the innovated practices. However, Allah Ta‘ala has taken the responsibility upon Himself to preserve this deen of Islam in its pristine form. Therefore, He sends a revivalist in every century who will trim and shave off the innovations that people introduced into Deen.
The ‘Ulama explain that the effects of innovations are worse than sins, because sins are such that the perpetrators regard it as wrong and hence they may repent one day from it. Whereas, they regard an innovation to be an act of virtue, hence they will never make taubah from it.