The World Bank and IMF only exist to perpetuate a capitalistic system whereby entire nations are subjected to economic exploitation and political submission. Their only real purpose is to further aggrandize the established elites in charge of this clandestine economic empire.
They are necessary for the world economy because the world economy is based around aggrandizing less than 1% of the population over the lower 99+%'s economic well being. The economy is already in shambles, because it's inevitable that a capitalistic economy destroy itself by nature of the greed that drives it.
If you really look around, most of the jobs that exist today aren't really necessary. Banks and Stock Markets produce nothing and yet account for millions of jobs on their own. The vast majority of industrial occupations could be eliminated through automation. Managerial occupations thereof would also vanish, and most of the rest of the service industry could be automated if we put a nominal amount of resources into it. The military is only necessary in a world based around nation-states. But that would leave a lot of people without jobs and cause a total, near instantaneous collapse of the global capitalist economy and hegemony. So people work several dead-end jobs, support their nations and religions and "free market", and are stripped of the leisure time they could be having, while potential alternatives to this insanity are constantly marginalized or assimilated into the capitalist system....
The economy is already dead to everyone except the kings and oligarchs of the capitalist establishment, and sooner or later this will catch up with them too. It's just a matter of time before the system destroys itself, and we had better come up with an alternative before things reach the tipping point.