I think the issue here is that sanctions require usually time to really take effect. The government is already installed by the time they come. The dictators and their cronies are shielded and live lo comfortably.

The population is either brainwashed or brutally repressed when it complains (particularly eliminating leaders).

It’s hard to make a case for sanctions as the solution as there are plenty of counter examples: Cuba has been heavily sanctioned for over half a century and little has changed no matter how dire the situation gets.

I wish they worked for sure, because what other resources you have against a nuclear power?

Edit to add: also, sanctions have exceptions (usually to shielding the sanctioning countries from suffering consequences, as in this case with Russia and the energy related transactions, with the effect of keep that money flowing for Russia).

And these tyrants workaround the sanctions in many cases with the help of other nations.