You could still have the Great Wheel planes even if you scrapped the mortal souls going to them as an afterlife. It would be planar dimensions you could go to with gods and outsiders and weird planar alignment concepts and high fantasy setting concepts.I think that's right. I also think it's inescapable, though, so I don't even bother to look for consistency in this stuff. They could have made it consistent right from the start by keeping the afterlife in the afterlife, but that would've precluded using the gods and planes in adventures, which I imagine was the whole point. My hunch is that inconsistency was the price for building out all this adventure-ready game-space.
It would've been a lot more logically coherent and consistent to keep the afterlife in the afterlife, but where's the fun and adventure in that? Orpheus isn't famous on account of a spelunking expedition, so they fudged the line between the afterlife and the mortal world.
4e kept the afterlife in the unknown afterlife instead of in the adventuring planes. It still has lots of fun god and planar stuff in my opinion. The original 4e set of 1-30 modules culminates in planar adventures with Orcus trying to take over the Raven Queen's death portfolio and turn all of the afterlife into unending Undeath for everyone. Also the 4e planar books such as the 4e Manual of the Planes, the Planes Above and the Planes Below, and the Demonomicon are all generally highly regarded fun D&D sourcebooks.