In the 1918 short story "The Spider's Thread" by Ryunosuke Akutagawa, buddha looks into a pond and sees hell on the other side. Given the amount of buddhist symbolism in Fire Emblem Fates, I don't consider it a stretch to claim that Azura going through water to reach Valla was inspired by this story. In this interpretation, Valla would be hell. The idea of Valla being hell is supported in the text given that most of the conflicts within Fates' narrative stem from there, but it's also supported both on a meta level and in the gameplay.
To start with the meta element, the point where Corrin and the rest enter Valla is also the point where the story becomes truly horrible (hellish, you could say). All the ridiculous plot contrivances and poor character writing come to a head here. Who's leading Hoshido while all its rulers are gone? Iunno. Why does Corrin trust this child despite only ever meeting brainwashed puppets in Valla? Iunno. Why do we get heart to hearts with the Hoshido parents but not Garon despite him needing the humanization the most? Iunno. Why are the brothers the only siblings with a shred of plot relevance? Iunno. Why does Azura completely lack agency and only exist to point Corrin to the next plot point? Iunno. Rev's story could have been generously described as rocky at the absolute best until now but with the main characters taking the plunge into Valla, so too does the quality of the story.
The gameplay is also relevant here. The map gimmicks in Valla are horrendous. Constantly waiting around for platforms to move make the maps slow and tedious and when it's not trying to be a platformer the maps are often incredibly plain with enemies interspersed randomly. Awakening also had bad gameplay but at least that was easy to get through, Revelation is just a slog.
To start with the meta element, the point where Corrin and the rest enter Valla is also the point where the story becomes truly horrible (hellish, you could say). All the ridiculous plot contrivances and poor character writing come to a head here. Who's leading Hoshido while all its rulers are gone? Iunno. Why does Corrin trust this child despite only ever meeting brainwashed puppets in Valla? Iunno. Why do we get heart to hearts with the Hoshido parents but not Garon despite him needing the humanization the most? Iunno. Why are the brothers the only siblings with a shred of plot relevance? Iunno. Why does Azura completely lack agency and only exist to point Corrin to the next plot point? Iunno. Rev's story could have been generously described as rocky at the absolute best until now but with the main characters taking the plunge into Valla, so too does the quality of the story.
The gameplay is also relevant here. The map gimmicks in Valla are horrendous. Constantly waiting around for platforms to move make the maps slow and tedious and when it's not trying to be a platformer the maps are often incredibly plain with enemies interspersed randomly. Awakening also had bad gameplay but at least that was easy to get through, Revelation is just a slog.