I was bought up Catholic and left the church as an adult. I was educated in a Convent for several years and had met some very inspiring nuns (and some uninspiring ones too).
The reason I left the church (although, as pointed out above you can never truly leave), was related to my growing agency in my life and my feminism.
My definition of feminism is : 'women matter as much as men' . My experience of Catholicism is that within the church this is not so.
My brother (who was very indifferent to religion from an early age) got to be an altar boy, I (who was much more fervently Catholic) did not. ( I know that this has now changed). To me at the time, i didn't understand this inequality.
Then our local parish priest spent a lot of time sucking up to rich widows and got himself several mentions in wills, so had a rather nice car. It was a parish joke. This oppotunism also didn't sit well with me.
At school I had an incredibly intelligent and wise nun as a headmistress. She was amazing, but it occurred to me that this is as far as a woman could get in the church even with her intellect. And just limited to girls schools and shaping girls minds. She was worth 10 of the fancy car owning priest, but he was her senior.
Then there was an acceptance into the church of married Anglican priests, who left as they didn't want women priests in the C of E. One became our parish priest. I find myself looking at his wedding ring during his sermon thinking 'why do you disagree with a women being able to do what you are doing now. '
Then I got involved in my career and was dealing with male heavy hierarchies at work, which I found limiting to me and set a mysoginistic environment generally. One of my job search criteria was some women in senior positions and not just the inevitable one in HR. Then I had a sort of revelation that the Catholic church was such an institution, with my headmistress the equivalent of the senior woman, but only in HR.
Then there were all the child abuse scandal and the way that they were hushed up. One of my friends parish priests was one of these men. When the church found out, he was simply moved to another parish and it was hushed up. This was how abuse was dealt with. Appalling.
I have always disagreed with the stance on contraception and abortion and don't know anyone under 60 who had ever paid attention to it, yet it is part of the rules. Why have the rules if you know they are unworkable and not followed? And of course these rules primarily affect women.
So all of the above(and several other small but significant things) gradually built up a picture over time that women and girls (and children) simply do not matter as much as the men. And it doesn't make for a good environment and breeds bad behaviour.
I know that there are changes (eg girls can be Altar girls) but it has been small irrelevant gestures and as the church ages and weakens.
I actually admire those feminists who care enough about the church to try to change it from the inside, but my experiences mean that I simply don't care enough about the church to want to try.