why there is no light type instead we get fairy type.

[tetrahedronX901]

Necrozma is the big example of we need a light type, but Necrozma does not look a like psychic type or a fairy type because because it's the concept of light and is a prism like creature which represent light for some reason., instead we have fairy type which is not light but a force of goodness? and photon geyser should be light type because nothing screams fairy or psychic just raw light energy.

is the light type too redundant?

and why dark type is the immoral type? like it's associated with the concept of darkness?

like there is rock and ground type which is redundant too? because they are similiar too each other?

 

[Corveone]

Because Fairy encompasses Light and other concepts so it was easier to retroactively add to existing Pokémon like Clefairy, Togepi, and others.
And because light based moves had been associated with different types even before Fairy existed: Power Gem, Solar Beam, Flash Cannon, Confuse Ray, Light Screen...

"Dark" is actually the Evil/Sinister type, it's just called Dark because the English translators decided to call it that way. The concept of this type is about fighting with cheap/dirty/dishonorable tactics, as a counterpart to Fighting which is generally based on respectable martial arts.

 

[tetrahedronX901]

Well there is ground rock type which are similiar