It is less corrupted. Without capitalism personal connections is the only source of power, so the only ones with power would be politicians and their friends. With capitalism we create another bastion of power, the capital class. Communists are politicians who don't want to share power with the capital class and instead hog it all for themselves. We all know what happens when politicians has no group to oppose them, everything goes to shit.

Maybe you could think of some other system where personal connections isn't the only source of power, but so far democratic capitalism is the only thing we have.

Edit: As for your scenario with capital paying money to influence politicians. The alternative is that the politician already have all the power (and money), nobody has to pay them. To me it is better that there is some corruption with money going to politicians rather than politicians just having all the money from the start.