For many religious people, raising their children in their faith is an important part of their religious practice. They might see getting their kids into heaven as one of the most important things they can do as parent. And certainly, adults should have the right to practice their religion freely, but children are impressionable and unlikely to realize that they are being indoctrinated into one religion out of the thousands that humans practice.
And many faith traditions have beliefs that are at odds with science or support bigoted worldviews. For example, a queer person being raised in the Catholic Church would be taught that they are inherently disordered and would likely be discouraged from being involved in LGBTQ support groups.
Where do you think the line is between practicing your own religion faithfully and unethically forcing your beliefs on someone else?
This is just useless gatekeeping. You don’t have to be a parent to have a perspective on how people should be raised. Every adult was a child at some point, so everyone has an experience to relate about how they were raised and the flaws they see in different approaches from their direct experience. Parents aren’t the only party involved. Not only does it take a village to raise kids, but other people are ultimately affected by parental decisions (e.g. Jennifer and James Crumbley).