No doubt technology and demographics play a significant part, but I think you're selling the effects political policies on the economy just a tad short.
Not really. And noticed I said *fiscal* policy -- those concerned with taxation and government spending -- as opposed to economic policies or politics more generally.
The biggest things you need politically are the basics and good institutions...
-- political stability
-- the rule of law
-- property rights
-- predominantly private ownership of the means of production
-- a reasonable regulatory environment
-- stable currency
-- mostly open trade relationships
-- dependable, functioning law enforcement and courts (civil and criminal)
Once you have those, the most important things towards growth are ones completely unrelated (or at least only tenuously related) to politics. Those are basically the big, structural things that make up our world and human society beyond anybody's control...
-- technology
-- demographics and migration
-- changing cultural trends and tastes
-- resource endowments (water, minerals, land, etc.)
After that, in this hierarchy, the next most influential factor towards economic growth would be monetary policy, especially in the short- and medium-terms.
Fiscal policy is a distant fourth behind all of those. To use an analogy, you can sluice off some of the water from the stream and move it around with fiscal policy (thought not much), slow it down or speed it up with monetary policy, or evaporate the river entirely with bad institutions, but for the most part, the course it is going to take is what it wants to take.
Even powerful political leaders and central bankers are mostly along for the ride.