One of the severest blows against Aga Khani Ismailis’ efforts to disguise themselves as the ‘second-largest’ group of Shia Muslims was when the Shia Grand Ayatollah Allama Shaykh Muhammad Hussain Najafi clearly declared them outside of the fold of Shia Islam and Islam altogether.
Allama Muhammad Hussain Najafi is known in the Twelver (Athnā‘ashariyyah or Ithnā‘ashariyyah) circles as being as non-Takfiri (one who does not declare other sects as outside the fold of Islam) and has earned further respect by being included int he lists of “The 500 Most Influential Muslims” in 2010 and 2011. He is also one of the only two Twelver Shi’i aalims from Pakistan who have been elevated to the status of marjiyyat. Marjaʿ (Arabic: مرجع) is a title provided to a Shia authority – a Grand Ayatollah who has the authority to make legal decisions within the confines of Islamic law for followers and less-credentialed clerics. After the Qur’an and the Prophets and Imams, marājiʿ are the highest authority on religious laws in Shia Islam.
Here is the video excerpt from the question and answer session:
Allama Najafi clearly explains in the above that the reason for ruling Aga Khani Ismailis out of the fold of Islam is their rejection of all the tenants of Islam such as prayer, fasting, zakat and Hajj.