Photos of truly massive piles of spent artillery shell casings helped this click for me [2]. Even if the artillery detonates 99% of the time, we're still talking about hundreds of thousands or maybe millions of unexploded shells.
People will be stumbling into unexploded butterfly mines and cluster munitions in Ukraine for generations.
[1] https://www.youtube.com/watch?v=YNIBE64CAgs
[2] https://64.media.tumblr.com/37a01168a1c386fa1657ae35ce0d0508...