So in short, it's a crapsack world, and campaigns rarely involve fixing it?
There was a campaign that Puffin Forest did where there was a treaty between celestials and fiends that was stolen reigniting the war with the intent that the upper planes would win. But the guy who did that was the antagonist. The players were trying to preserve the status quo.
D&D has hell. It used to be that the fastest-reproducing races were also evil, sending more and more people to hell.
Looking it up, the creators were Christian, so maybe they thought real life was even worse, but D&D was always intended as a crapsack world. If you want to play one that isn't, great. Just be prepared to rewrite some major lore.
They could make a program where you give it the players' character sheets and the encounter and it simulates a bunch of battles to see how they do. But failing that, you could make CR be a good average, where you could just look at that and adjust based on what the strengths and weaknesses are. I haven't actually played 5e so I don't know this from personal experience, but my impression is that they haven't done that. Some creatures just don't have a CR that matches them in general.
There's also no system for figuring out the CR of an encounter with an arbitrary set of monsters and enemies with class levels.
Education and maturity are not the same thing. Also, if you live for hundreds of years the rational thing to do is work hard at the beginning so you can live on the interest for the rest of it.
But you only actually sleep for six of it. You spend up to two hours of it doing a light activity like keeping watch and reading. And yet you're still fully rested and healed of all damage.
That's based on the idea that vampires are weak to silver, right? In D&D, they don't seem to have that weakness. It should be werewolves, devils, wights, jackalweres, wraiths and night hags that don't have reflections in silver mirrors. Also, the mirror in equipment is steel. The only way to get a silver mirror is to learn Sanctuary and have a component pouch.
So in short, it's a crapsack world, and campaigns rarely involve fixing it?
There was a campaign that Puffin Forest did where there was a treaty between celestials and fiends that was stolen reigniting the war with the intent that the upper planes would win. But the guy who did that was the antagonist. The players were trying to preserve the status quo.