I feel I may be in a minority group, as I was never religious, I have often thought about how I would feel if I had been indoctrinated when young and had escaped from it in my 20s or 30s I think I would be very angry, betrayed and annoyed to have wasted so much time and money on a fantasy, although it is hard to imagine…
I did not feel betrayed or angry for being lied to. I attribute it to a long line of brainwashed family members continuing the cycle of brainwashing with each generation. Nobody knows they are being brainwashed and sincerely believe they are doing what's best for their kids. I don't think I ever wasted too much money as I am/was frugal and would rarely give money into the collection plate.
Interestingly, I actually felt jealous of the religious as they didn't lose their sense of community, were not shamed for their mindset (aka leaving the church/abandoning the beliefs) and they have a comforting story to tell themselves when loved ones die. I lost that and am still shamed and lost "friends" once I came out with anti-theist rhetoric on my facebook. But also, my family did much more fckd up shit than indoctrinate me soo the indoctrination is the most minor thing I'd be angry and betrayed about.
Possibly not as hard to imagine as you think. Although I grew up in the JW cult and was often persecuted as a child because of it, I had a neighbour who was an atheist in a family of atheists and he was equally persecuted for his lack of belief by the kids who were from homes which adopted the majority religions.
I have often wondered what it must have been like to grow up as a Catholic with all the ritual bull shit that goes along with most of the major religions.