In many cases they my not be practicing and attending church but their beliefs are still there. In my personal case I haven’t attended church in years, because I have seen too many organizations that dither too much in political/social/gossip activities and not enough in the Word. Sorta the way the Rinos have abandoned conservative principles.
People are sinners blindly following any person or group of people will eventually lead us away from the path in the same manner that a minor compass error uncorrected will eventually result in being miles off course.
I have continued to read the Bible and literature about the meaning of the Bible - the literature varies as well, but this is where I believe the personal relationship with God comes into play.
We can never 100% understand God he is too vast and powerful and wonderous for our measly little minds to comprehend, but we can have faith and endeavor to know more and strive to adhere to our understanding of his Word.
I cringe every time I see an American flag in a church. I wonder if the seven churches had their nations flag in them. ;)