I have sample of friends who leave Islam and convert into agnostic. They dislike the religious institution, according to them, soccer fanclub such Viking Persib and Jakmania Persija are religion too, and they have their own holy war, monthly or annualy. So after left Islam, they never convert to Catholic or Buddha, or any formal religion, they chose become lone spiritualist instead.
Why? They thought that anybody could connect to Creator directly, not necessarily joining any institutionalized religion. They saw many fakes act of corrupt while still appear as religious person, as conformity with culture. In Indonesia, appear as religious is necessary action to survive for better life, and some of my friends thought it is a double standard, no integrity.
Religious people will never totally surrender to God, because they have a band of brothers who protect their life, no real threat. While the main core of Islamic teaching is the art of totally surrender to God.