While much of you write is true, that members are cruel to former members, that is not the main reason people don’t return to the Church.
The #1 internal reason people don’t return to the Church is: integrity.
The #1 external reason people don’t return to the Church is: the Church is largely false, and puts people in service to falsehood.
You can see how the internal and external reasons are two sides of the same coin.
The Book of Mormon is proven fiction. The “keystone of our religion” is fiction. Participating in a community and a culture that places everything, your marriage, your family, your community, in the service of perpetuating proven falsehoods, that the Book of Mormon is “true”, and that Joseph Smith had any prophetic foresight or godly authority, that by itself is painful for anyone with integrity.
That is the reason people don’t return to the Church. Despite all the good things found in the Church: love, charity, family, strong community, education, emergency preparedness, etc., when you make true human principles subject to falsehood, the whole thing becomes corrupt.
I am grateful for the many positive lessons I learned as I was raised in the Church. “Honesty is the best policy” is perhaps first and foremost, and that is why I can never return. I will not lend my strength to support untruth.