Except that's exactly what it does. The whole point was to make the game easier if a player did well and make it harder if they did not; and because BOTH ends of tendency have rewards, either is worth getting. The only time world tendency mattered is when you legitimately wanted whatever items it had in store at either end, in which case you either killed yourself a lot or were extremely careful. What happened to that ever popular Dark Souls saying "Git gud"? Just as well, none of the items you got were required to beat the game. Hell, they only either made the game slightly easier or were used for incredibly specific builds.
While it's true that Firestorm/Wrath of God are extremely damaging spells, they also take up a TON of mana and memory slots, not to mention its extreme wind-up time. As another anon pointed out, it was a glass cannon.
How can you legitimately be upset with 'infinite healing' when people will farm Humanity/Double Humanity for the express purpose of using it as a healing tool? Gods damn, at least grass that filled up 100% of your health was fuckin' rare in Demon's Souls.
Except it is. It forces you to be careful and considerate when choosing the weapons and armour you need to fight, so you CAN'T just mix and match, you actually have to be careful. Besides, if you level your vitality past 15, you should be able to carry most of the level just fine, they even give you a specific RING to help you out in case you can't.
If you actually NEED to sort through a bunch of weapons before a battle, you don't need weapons, you just need to strategize better.