As long as good politicians feel they'll be disadvantaged if they aren't selling themselves like the idiot ones are the good ones will line up for the money.
Certainly it's better to outlaw it rather than to simply allow it to happen. You will never catch 100% of the people breaking the law, but you can create an environment of transparency and accountability to help and you can make it costly enough for those who are caught to make the next person reconsider risking it.
lobbying is illegal in many countries yet it does not make corruption dissappear, far from it. Its like the war on drugs: it makes cartels stronger, if anything.
Certainly it's better to outlaw it rather than to simply allow it to happen. You will never catch 100% of the people breaking the law, but you can create an environment of transparency and accountability to help and you can make it costly enough for those who are caught to make the next person reconsider risking it.