Sanctions have been shown to be a very ineffective, but low risk tool to apply external pressure. There is no way to apply sanctions in a way that truly hurt the responsible rulers without affecting the general populace. As the rulers by definition have power, they will simply be able to force lower, non sanctioned ranks to do what they want, circumventing the sanctions.

In addition, the hope of blanket sanctions is that the populace looks their economical suffering to the bad decisions of their leaders and speak our act against them. This rarely ever works, as state propaganda easily spins it to blame the international community being influenced by the state’s enemies. The first to suffer will always be the lowest strata of society, which usually is least involved in international affairs.

It’s the same reason any kind of external punitive action against civilians (e.g. city bombing in ww2) doesn’t work.