The Taliban has multiple income streams which have financed their operations for the last two decades; primarily the drug trade, and resource extraction (mining). Private citizens from Saudi Arabia, Pakistan, Iran and other Gulf nations also inject huge funds into the Taliban. They have pretty robust finances.
And so we are clear, the soviets didn't fight against the Taliban, they fought against the mujahidden who (until the US led intervention) did not have the finances or organisational capacity to overcome the government or its Soviet support.
My argument is more that at the end of the twentieth century, it would have been much easier for the ruling government and the USSR to overcome the mujahidden had the US not interfered and, if that had happened, Afghanistan would have have in a much more prosperous and secure place than it is now.