Currently running a 5e campaign in the Nentir Vale. I'm a big fan of the setting as a PoL sandbox setting.
Overall, there was a lot of influence from real world mythology, particularly the motif of the Chaoskampf, that I particularly liked. One of the prevalent ideas within the "Chaoskampf" worldview in a lot of West Asian (e.g., Judean, Babylonian, etc.) and North African (e.g,. Egyptian) ancient worldviews is that 'chaos' remains a pervasive threat in the world that could potentially undo creation. This requires the vigilance of mortal forces of order and stability (e.g., kings ruling, cities protecting, priesthood performing sacrifices, etc.) to bring and maintain order in the world. The threats of chaos experienced in the mortal world represent a microcosm of the grander cosmological macrocosm.
So you got smatterings of Greco-Roman, Levantine-Mesopotamian, and Indo-Iranian mythology in the mix. Plus, similarities with the beloved Scarred Lands campaign setting, for obvious reasons. What this meant for the Nentir Vale is that everything in the world had a "place" within the cosmic struggle, even if you are only seeing it from the grounds-eye perspective of mortals in the countryside. THAT is sorta what living in a world with a mythological worldview should feel like.
That's what I liked about the Nentir Vale. It felt less embedded in the Good vs. Evil moral axis, but, rather, on the Law vs. Chaos axis. The order of the Vale exists under a threatened state by chaos. The empire of Nerath had collapsed under a constant onslaught of invading gnolls. The wilderness is chaotic. One of the major settlements, Fallcrest, had been overrun by orcs about 80 years prior. So there is feeling of vulnerability even when one resides in these "Poli of Light."
I could keep going, but I'll just say that there is a lot that I absolutely love about the Nentir Vale from the perspective of a GM. I'm not entirely sure if Mike Mearls "got it" when running his Nentir Vale campaign. I do think that Mearls had some GREAT innovations (e.g., the god Torog pulling things down into the Underdark and pushing things up from the Underdark), but the idea of having the gods all be ascended mortals was almost a shark-jumping moment that undercut the entire mythos of the Vale. Todd Kenreck, who took over for Mearls after he left the game, seemed to have far less of an idea what the Vale setting was about - I believe that he even just nuked Fallcrest - and I think he even just teleported the players to Forgotten Realms instead.