I think people really oversimplify all radical, religious, forms of terrorism. Many of ISIS beliefs are those which are shared with many other Islamist groups - including Hamas, Houthis, taliban. This includes, repression of women, LGBTQ+, disabled groups and other religions. Anyone who thinks otherwise is incredibly naive.
Separately, if you look at which Muslim councils or groups have condemned the above groups, you will quickly realise it is Shia condemning Sunni (as the case with ISIS) and Sunni condemning Shia (as is the case with the Houthis). That, in itself, is a problem. People disassociate from the acts of other off-shoots of their religion - and say it’s not to do with them, whilst turning a blind eye to those who commit similar crimes who are part of their (Sunni or Shia) branch. It’s incredibly unsettling. In layman’s turns, it’s like a Protestant saying ‘we condemn pedophilia in the Catholic church’ whilst ignoring that the Protestant church has its own issues with pedophilia.
What happened to the Kurds, Yezidis, Christians and Jews, alongside the Shia Muslims, in Iraq and Syria was awful. But, this began 10+ years ago. Sadly (and it doesn’t make it right) the world has moved on to the next crisis.
I’ve often thought that without religion, the world would be a better place.