Not all drugs are bad. There are some that are obviously terrible and ruin lives. There are also some that help with a wide variety of physical and mental health issues though.
Even if you’re just thinking all drugs are bad, dumping people in jail for drug use/possession doesn’t fix anything. Time and money would be better spent on rehabilitation in that scenario.
Decriminalizing possession helps keep people out of jail, opens the door for proper studies on effects, and can help people with chronic conditions. I have heard that microdosing shrooms is apparently helpful with treating depression. It would be nice to see more information on that.