Iruka is very useful in the right lineup.

In a Konoha lineup he is deadly due to his shield, boost and turn 1 interrupt. You can pair him up with Danzo as a LM or with a Hashirama team.

It even stayed relevant after han and Roshi due to the fact that he has a boost without a barrier (no roshi break) and he can interrupt han if he is placed first in a lineup. All of this added to his utility in ninja exam and world boss makes him a must have ninja for end game, which fortunately can be gotten by refininf ninja fragments.

A bit harder now that ranked points supply has been cut by half but still, good ninja.