It's difficult to say to how us, human mortals from Earth, would act if placed in a D&D world.
On one hand, the gods there are provably real, on the other, they're flawed polytheistic gods, not perfect beings. They're often former mortals.
On one hand, great magic power can be obtained by serving the gods, on the other, it can also be obtained by studying the arcane arts, making eldritch pacts, or just by being charismatic performers. You can obtain demigod-level power without ever caring about the gods.
I do think that the setting makes enough sense as is. I think it's a believable fantasy setting.
Could the writers just say "screw it, from now on faithless mortals aren't punished, and that won't have far-reaching consequences because the faithless are going to be few and far between, anyway"? Sure, they could if they wanted to. At some point during 4e, the writers pretty much deleted more than half of the FR pantheon, because they felt like streamlining the setting was a good idea. They can do whatever they want.
My question is, would removing the wall make for a better setting? I'd argue that it wouldn't.
The wall of faithless is an element of lore that makes the Realms more interesting and unique. The setting would be lessened, not improved, by its removal. And really, why remove it? What do we gain by removing the wall? I know what we would lose: a fascinating piece of lore and a number of interesting plot hooks.
What do we gain?
The Morality of the Gods of Good, Justice, and Mercy.
As it stands, with no clear answers on why the Wall exists, who opposed it, why, when, and why it continues to exist.
One thing I liked in the Wiki article I linked was a brief mention in a book, which seems to have been retconned, that Kelemvor changed the Wall, and made it a massive soul mirror to reflect a souls faults back on itself. That makes for not only a good story, but a legitimate reasoning behind the Wall.
Originally made by the Cruel Myrkul, who was God of the Dead, it was built as a torturous punishment for the False and the Faithless. Not because those things were crimes, but because the other gods could not lay claim to souls that rejected them, leaving them to Myrkul's cruel designs. Then, with the rise of Kelemvor, as the Judge of the Dead, he exercised his power over the Domain and remade the wall into not a tool of torture, but a tool of Judgement. Perhaps again it is mainly targeting the False and the Faithless, those who fall to no domain but Kelemvor's, to allow them to seek understanding and redemption, to face their faults and hopefully rise above them. Maybe it does still drag down and destroy those who are overwhelmed by their own darkness.
And why did no Wall exist before Myrkul? Because Jergal did not care what happened to the souls of the Dead. He sought no punishment nor judgement, only endless accounting.
That to me is a much tighter and coherent story. One that we almost got, but was instead tossed aside for continuing the mess we currently have.
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I'm complicit in utter evil quite frequently. I still make an effort to do good deeds on the regular. Does it balance out? Probably not, but that's a question for millennia of philosophers.
And you are also not a God whose entire existence is founded on not being complicit with Evil.
Torm is the god of Courage and Self-Sacrifice, of making that Last Stand, even if it will kill you. How can he embody that while at the same time standing by and watching injustice continue.