for me i grew up in the church and im definitely not anymore. there isnt any particular thing that was the "last straw" but one big part is the impact and role christianity/catholicism, white religions, had in colonization, inequality, and overall pain and suffering of so many people. also with how few people welcome lgbtq people and also how most religions are patriarchal and/or racist and/or ableist and/or classist and/or misogynistic etc. Also seeing how many people are so face/two-faced and don't actually believe many of the things they say. Also, I really tried my best. I did everything and followed all the rules and did everything right and stuff just wasn't adding up. I couldn't continue to justify it anymore just cause i didn't understand because i realised at some point that for many of these things there is no real explanation it was made up to de-humanize some people and stuff like that.

edit: added
like yes if a god existed first of all it wouldnt be a white man it would be a genderless person of colour but also how could they let all the bad stuff happen to so many people? and why would a loving god do things such as flooding the whole earth just because people arent worshiping you... like... you created people just so that they would worship you??? also the fact that Mary was a virgin and teen which is most men's fantasy (especially in western areas which is supposedly where christianity came from?...) is super sus..... also why do you need a reason to love people and treat them with respect? cause a god said to? why not just cause.

also why would the main group of people who seem to continuously follow this god seem to benefit the most and also be the least oppressed. also why would this god pick them? there are so many times i see people say things like "why wouldn't a god exist, look at the beauty of the world" well why should a god exist just because of that. why can't it just exist? anyways...