Kankuro was very comonly used and people even used to cry he was op at start of game, he was meta team for 4 mains, Earth/Water/Wind/Fire all had teams with him that worked well, Kankuro + Hinata combo was meta for few months, i remeber i used to get bully in swb runing Kankuro/Hinata/Kakashi for a while think he fell out of favour when they reworkd light main root and people started runing curse team, old root used to boost attack then it got changed to +100% resistance and made that team rly annoyin and tanky.

Also it wasn't really a nerf, it was a change. He had 'summon puppet turn 1' as a passive skill, they removed poison from mystery and added his summon puppet to mystery and they gave him a new passive +20 chakra per chase. So he traded poison for ability to get 40 chakra per turn.

And yeh like previous guy said he was changed looooong time ago, bout same time they nerfed(murdered) Tobi, maybe 2017, he was still relevant then.