You should tell this to countries that have crude oil as their natural resources and they totally depend on it as a source of income generation. Crude oil exportation has made the leaders of my country to be lazy, they don't care about income generation from other sources. They don't care what happens when their crude oil is no longer needed. Ofcourse they have embezzled enough money to give them and their families good life in Europe and America.
Electricity will be the alternative to crude and gas, most things that are powered by refined crude oil and gas will be powered by electricity.
Even nations like Saudi Arabia is aware that the oil and gas money will run out eventually, and they keep on investing into other stuff. With the money they make from those, they are putting investments all over the world and either buying companies outright, or buying shares of the companies.
That way, they own bunch of super wealthy companies all around the world, that will continue to make money even if they have zero dollars left from the resources. That's not going to be enough just for now, but it won't be nothing neither. We should be seeing how this could be a better situation for the long term and if they keep this up, and keep buying, they will have income that will be enough for them and do fine when they have to.