Have you read his books? he thought it was completly fine to kill all Sunnis who didn't agree with his views and take their women as slaves, since they were (in his eyes) mushrikeen. His followers in 1803 massacred all the Muslim men of Tai'if and took their women and children as slaves. The same thing happened in the 1924 Ta'if massacre.
He didn't call for a refrain from innovation, he called for an innovation of his own. How does a man who live in the 19th century know how the Salaf (three blessed generations) lived while he rejects all Scholarly links and traditions that originated from them? the answer is that he simply read the Qur'an and the Ahadith in a literalist fashion, while rejecting 1400 years of Scholarly interpretations.
MIAW invented the notion of rejecting Kalam while only relying on Ijtihad. This was never a belief held by anyone before him, not even the Sufis that ironically inspired him, the Kazidelis who followed the beliefs of Ibn Taymiyya (rahimahullah), who also identified with and praised the Qadariyya Sufis, but was critical of their wider acceptance of Tawassul. MIAW took this to an extremity and refered to the *majority of Muslims* as mushrikeen, not even Ahl Kitab. This is why extreme Takfiris eat the kosher-meat slaughtered by Jews but will never touch the meat of Sunnis or Shi'ah. Thus, MIAW was rightfully seen by his father and brother as an innovator of his own and his own family wrote fatwas and books refuting him.
he claimed the majority of Muslims are mushrikeen?
so can you show where he says that?