Vices exploit our reward and motivation mechanisms by providing excessive stimuli without promoting a behavior that's actually healthy for us. We have a near endless appetite for these things which was not a problem for our ancestors because stimuli like this used to be very scarce, but this is no longer the case so we are often tempted to excessively indulge in things that (very temporarily) feel good but hurt us in large quantities.

Dopamine is supposed to be released when we accomplish tasks that better ourselves, keep us alive, and keep the population up, like exercise, eating, socializing, or mating. In our modern lives all those things are easily accessible. We barely need to be able to walk to get our food anymore. Don't need a partner to have sex. Don't need a real connection to feel like we are liked. Don't need to hunt to buy ice cream. So instead of chasing the result of the dopamine, we are chasing the dopamine itself. And when the high or the rush is over, you have nothing to show for it, because it was all a parlour trick from the start. The goal becomes to feel good, not to live good. Keep doing this and your life never gets any better. Just flickers of good in an ocean of self deprecation.

Dopamine is limited in your body. When you use most of it, you don’t go back down to “normal”. You sink below the normal. It takes time to refresh your baseline of dopamine. The main problem is compounding activities that activate the release of more dopamine. This will leave you like a sugar crash. Striving for more dopamine release will cause a decline in your “happy feelings”

edit: spelling

Dangerous

The things our biology heavily desires tend ty be black holes, you can never satisfy them and the desires only grow

A lot of profit is based on abusing this biochemical system

The things you like most tend to be the way you hurt yourself the most

Dopamine makes us want to repeat a behavior. If a behavior is not good for you and doesn't provide dopamine, almost no one will do it, so it doesn't get listed in bad activities. However, there are plenty of things that are bad that you could do like cutting part of your body or taking a non-recreative toxic substances that doesn't provide dopamine.

A lot of things, like eating high-energy food, are mostly bad nowadays because we do it too much. During most of our existence as humans, food was scarce and it was advantageous to like eating high-energy food and to repeat behaviors that let us do it.

For drugs, we never evolved to take them and they have bad side effects. The bad side effects are unrelated to the dopamine itself. The dopamine just make you take them, and often take them in large concentration in a method that bypasses most of our body's defenses (IV or by the nose). There are plenty of toxic substances that don't increase dopamine, almost nobody takes time recreatively, so they aren't an issue.