The biggest question !!!

[Prabhoo]

Why are sasuke and kakashi proficient in all the5 chakra transformation ??
Gai knows fire and lightning ?? WTF
Darui knows wind and earth ??
Practically everyone has got new Nature transformation !! Even Sakura has got some !!

 

[Oddity]

Your looking at the wrong Naruto Wiki.
I checked Narutopedia the most trusted one and it he doesn't know Doton.

 

[Mypower]

Kishi had to rush the manga.

 

[SMX]

Rinnegan allows you to use all 5 natures

Kakashi copied all 5 natures

 

[Prabhoo]

Rinnegan allows you to use all 5 natures

Kakashi copied all 5 natures

What about the others ??

 

[SMX]

What about the others ??

Gai for sure has fire its used in one of his gates attacks, lightning idk

Darui idk

 

[SharinganisOP]

What about the others ??

It's stated in the manga that almost everyone has at least affinity towards one nature. The only exception I know of is Lee.

Some are born with several chakra affinities as well. KKG users are the most notable.

Some are able to learn two or more extremely easily, like Sasuke and kakashi (of course the sharingan helps)

Others work hard so they can use additional elements that they don't have affinities to.