There is no one thing. Name one thing and it starts an avalanche of a thousand things. For many of us it doesn't start with one thing. It's more like dying, or bleeding out (as a member of a cult) from a million paper cuts.
The level of fakeness, pettiness, judgemental arrogance, fear inducing guilt tripping horse manure that pours out of their mouths is enough to make anyway walk no, run away from them.
I don't know about other countries, but in the U.S. (especially New England area) it was eye opening for me to see how those who should have been the most spiritual, the most cognizant of the need to live a simple life preparing for the great tribulation (the elders) were the ones with the biggest houses, biggest properties, biggest businesses of those in the hall. It proved to me that none of them really believe in any of it anyway. They hire poor pioneers (while either pretending to pioneer or not pioneering themselves) to provide cheap labor for their construction, landscape, cleaning business while they rake in the big money. Hypocrites!