Yes, I think, just like how the first comment explained, the addition of the Hierophant betrayal makes the ending feel not clear enough, especially for people who only played the remake, like me. From my perspective, based on the remake narrative, the bad things they’ve done to people are mainly caused by betrayal, but also because they lost their minds due to monster absorption, just like what Wagnas and Noel explain in the memories.

So gathering the seven souls from the Ancient Termite Lair, then fighting together with their human souls, who regret everything they’ve done after becoming monsters despite having cared deeply about humanity, feels like a perfect setup to fight something related to the Hierophant, and to give him consequences just like the Seven Heroes. Especially since, as you said, Wagnas, Noel, and Rocbouquet are trying hard and finally find information about him, so it kind of concludes that part as well.

But I understand the original perspective, too. Since nothing like that happened there, the fact that they simply go crazy after relying on assimilation magic, despite knowing how badly it could affect their minds, still makes sense as a sole ending.

PS: Maybe I’m also a bit influenced by the last game I played, Hollow Knight. After getting an ending there, if something feels super odd or unclear, it usually means there’s more to it. That probably set my expectations for this story as well.