Hyrule does have its own religion. The religion mainly orbits around the goddesses and the Triforce. This is known, for in many parts of the games, people are praying to the gods. It is also known that Hyrule also has its own version of the creation. However, Hyrule and Termina are two entirely different regions and religions.
Termina has the belief of four stone giants. The giants were perhaps a member of Termina's religion, but religion is very absent in Termina. In example, there are no true temples of worship, only dungeons and large facilities, not places that people have been known to pilgrimage and pay respects to the goddesses. Majora could possibly be the anti-god of Termina, even though the Hyrulian religion has not much for evil powers.
Now, Hyrule and Termina are two completely different, how many have spoken of, parallel universes. In example, the same characters in Ocarina of Time are shown, only to have different life experiences to those in Hyrule. The also thing that proves the flaw wrong is that Sharp and Flat were both present in Ocarina of Time, rather than Sharp being the only one present. It is with this that can further spawn into the idea of Termina being the exact opposite of Hyrule and its civilians. Although, in Ocarina of Time, after you had learnt the Sun's Song, both of them disappear, never to return for the remainder of the game. I do stick firmly on my position that Hyrule and Termina are the universal opposite of each other, thus causing this, in my beliefs, that only the Terminian Flat to be sent to the devil, while the Hyrulian Flat moved on in his afterlife. So, there no true flaw if you consider the Flat issue the only flaw. That would have to be redirected to the Terminian religion.