Guns are just tools that poke holes in things. We can't hold the manufacturers responsible for the way they get used.
Fentanyl is just a medical drug. The pharma companies aren't responsible for addiction.
I don't even disagree with your sentiment and I don't necessarily agree or disagree with my silly examples. But I hope you can see why some people would see calling them 'just instruments' can come across as washing ones hands from any responsibility.