They work for countries that kneecap themselves by being at the whims of capital and the market. Countries that don't constrain themselves like that can laugh at sanctions because they don't matter in that context.
Typically it actually looks like the opposite. When I look at, eg, North Korea or Iran - if I were going to try and make them wealthy it is mostly internal policies that are the problem and not external ones.
If North Korea set itself up with single digit % company and income tax combined with a strong rule of law, local education programs and a liberal economy it would barely matter what sanctions were imposed on them. A tide of money would flow in and they'd eventually be wealthy under their own power anyway if not. Although it isn't obvious why anyone would sanction a small well run country; there is a correlation between sanctions and incompetent governance.
- firstly, media attack ("they're dictatorship!", "they're genociding someone", etc), preparing population for stricter measures
- secondly, color revolution, which, if successful, puts puppet malleable government in power, and makes the country ultra-poor (most of the countries, where color revolutions staged by US/West succeeded, became significantly poorer)
- if color revolution didn't work, there's always an option to just bomb the country, because it's always ignored if all the international treaties and laws are ignored if USA or Israel bomb any other nation.