Lightning is more of the common trait shown so far.
Second is water and wind with Sumire and Mitsuki respectively having either or with Boruto
Yeah it's becoming too much. The entire class can use Fuuinjutsu too, go figure.
That is more of the class learning basic sealing at the Academy
like Kakashi stated due to times of peace the Academy is not just used by clans and the elite to make genins but also up their career opportunities.
The Academy today is more complex and better then the quick Academy of the past that needed genin on the field as soon as possible.
Kakashi even said that if they all failed to become genin that Konoha wouldn't suffer due to the times.
Now it is all about pumping out quality then quantity. In basic ability at least.