It's just really difficult to stomach that there's no reason. It's completely contrary to how our brains work I think.
Every few years or so I study different mainstream religions. One thing that jumps at you right at the beginning is how many of their loudest followers get them completely wrong. They all have nice ideas, I especially like some of the ideas of Buddism, the least theistic of the big religions, and can see why hipsters westernized it. But it's always possible to see the human influence, especially in the context of the time the religions formed, and if you do enough research you can also see how no religion is really static and how they shaped over time and are in fact quite fluid. For recent examples, e.g. protestants became sexually open in the 60s-70s in many countries and christian catholics had the rule from the beginning that suicide is one of the worst ways to reject god and a surefire way to end in Hell until to about the 90s, were the church basically changed it's mind somewhat and said "meh, sometimes people are just really suffering and mentally ill" and went bigger on the "mercy" factor and basically said if somebody unalives himself it's up to god if he can go to heaven but it's not impossible. Lots of catholics haven't gotten that particular memo which is funny because in catholicism what the church says is like, really important. It's a very "centralized" religion. This is in line with pretty much all of the mainstream religions, they all came around to recognize the mental health factor to varying degrees, because of the times we live in (first time in human history were mental health is even a thing, and it's a really recent development, to boot).
So basically, religions flipped from "You'll burn in hell!" to "Well, maybe God understands depression?" as soon as we understood neurochemicals.
There are even older examples where views shifted, e.g. acceptance of slavery, heliocentrism (that Galileo thing) or even polygamy and caste systems that are now rejected. So you clearly see that religion is something man-made, because they keep adapting to current societal, scientifical and cultural pressures. If religion was the result of the mandate of a higher being that's all knowing and all seeing, you'd think it'd get the rules right on the first go. Some religions counter this clear flaw with the fact that human's are fallible. Islam for example distinguishes between "Allah's perfect truth" and "fiqh", basically human interpretation. "Oh, how convienient" you say and you do have a point. You can always argue that the bigger plan is for religions to evolve to come closer to the "truth" and you'd never be wrong. In my weakest moments I even have looked for answers myself, but I could find none.
There's only one answer: We are meaning-craving creatures trapped in a universe that doesn't care.
And that's really it. It's so incredibly horrifying that nothing matters and everything is meaningless until we cease to exist that people came up with all this. It is literally easier to suffer for a higher meaning than to just exist in an uncaring and meaningless universe, even if that existance is objectively pleasant.
Is that Hell? No, it just is.
