Petrostates are thought to be vulnerable to what economists call
Dutch disease, a term coined during the 1970s after the Netherlands discovered natural gas in the North Sea.
In an afflicted country, a resource boom attracts large inflows of foreign capital, which leads to an appreciation of the local currency and a boost for imports that are now comparatively cheaper. This sucks labor and capital away from other sectors of the economy, such as agriculture and manufacturing, which economists say are more important for growth and competitiveness. As these labor-intensive export industries flag, unemployment could rise, and the country could develop an unhealthy dependence on the export of natural resources. In extreme cases, a petrostate forgoes local oil production and instead derives most of its oil wealth through high taxes on foreign drillers. Petrostate economies are then left highly vulnerable to unpredictable swings in global energy prices and capital flight.
That's what happened to Venezuela, just as it has occurred to capitalist petrostates as well. Oil prices plunged from more than $100 per barrel in 2014 to under $30 per barrel in early 2016, sucking Venezuela into an economic and political spiral. Conditions have only worsened since then. Add the US empire's economic embargo and it makes the crisis even worse. But eventually, Venezuela is going to recover, despite the sanctions.
Following your line of reasoning capitalism is a huge failure because most capitalist-run countries are plagued with gross inequality and poverty
(and they're not even being sanctioned by the most powerful empire in human history as Venezuela, Cuba, Nicaragua and several other communist countries are). Most of the failed states in the world are ruled by capitalist plutocrats and oligarchs. It took centuries for capitalism to replace feudalism and chattel slavery and likewise, socialism and communism won't replace capitalism until material conditions permit.
The European mercantile class didn't transform itself into the powerful industrialists of the 19th century, acquiring more power than the monarchs and feudal lords until technology (material conditions) allowed it to happen. Your reasoning is flawed, due to your anger and fear. Readjust your line of argumentation and be more consistent and fair in your critique.