Well FIFA are the world governing body they essentially set the rules and they are made up of the national associations so they can basically do what they want, anyone can create a football tournament.
A World Cup can work every 2 years if all the continental committees agree to stop their own tournaments so no more Euro's, African Cup of Nations, Gold Cup, Asia Cup or Copa America. These tournaments would need to go but why would these continents want to give up their tournament?
The main problem I see is for the teams that maybe can't get to a world cup but can get to a euros it just means these players never play in a major tournament to solve that problem they'd need to make the tournament even bigger which then devalues it.
The end goal here isn't to get a world cup every 2 years it's to dissolve UEFA and get these big european clubs operating under the FIFA name as the real money that can be made is in the club game and creating a version of the club world cup that replaces the champions league.