I don't think there is exists a magical political system that we set up and it magically protects us from corruption. Forever. Just like any system (like surviving in an otherwise hostile nature) it needs maintenance. Maintenance in a political or any social structure is getting off your bottom and imposing some "reward" signal on the system.
Corruption mainly exists because people have low standards for enforcing eradication of it. This is observable in the smallest levels. In countries where corruption is deeply engraved, even university student groups will be corrupted. Elected officials of societies of any size will be prone to put their personal interests in front of the groups' and will appoint or employ friends instead of randomers based on some quality metrics. The question is what are the other people willing to do? Is anyone willing to call them out? Is anyone willing to instead put on the job themselves and do it right (which can be demanding)?
The real question is how far are the individuals willing to go and how much discomfort are they willing to embrace to impose their requirements, needs, moral expectations on the political leader? The outcomes of many situations you face in society (should that be a salary negotiation or someone trying to rip you off in a shop) depend on how much sacrifice (e.g. discomfort) you are willing to take on to get out as a "winner" (or at least non-loser) of the situation? Are you willing to quit your job if you cannot get what you want? Are you going to argue with the person trying to rip you off? Are you willing to go to a lawyer and sue them and take a long legal battle?
If people keep choosing the easier way, there will always be people taking advantage of that. Sure, we have laws but laws also need maintenance and anyone wielding power needs active check! It doesn't just magically happen but the force that can keep it in check is every individual in the system. Technological advances and societal changes always lead to new ideas how to rip others off. What we would need is to truly punish the people trying to take advantage of such situations: no longer do business with them, ask others to boycott such behaviour (and don't vote for dickheads!, etc.) -- even in the smallest friends group such an issue could arise.
The question is: how much are people willing to sacrifice on a daily basis to put pressure on corrupt people? There is no magic here, just the same bare evolutionary forces in place for the past 100,000 years of humankind.
(Just think about it: even in rule of law, the ultimate way of enforcing someone to obey the rules is by pure physical force. If someone doesn't listen, ever, he will be picked up by other people and forced into a physical box and won't be allowed to leave. And I don't expect that to ever change, regardless of the political system. Similarly, we need to keep up an army at all times. If you simply go hard pacifist, someone will take advantage of that... Evolution. )
Democracy is an active game to be played and not just every 4 years. In society, people's everyday choices and standards are the "natural forces of evolution".