Politicians have been abusing earmarks for decades now. With that in mind, earmark abuse can be avoided by placing tighter restrictions on them. Politicians need to be closely policed and vetted to ensure that they aren't abusing the system. An impartial system of regulations on earmarks would curb most but not all abuses.
Earmarks are a tried and true method by which Senators and Representatives are able to help their districts and states. When you elect a Representative to Congress, the expectation is that they will do their best to help the people in the district. Earmarks are how they do that. A new airport, or a road, or a jobs project directly helps the people in the district. Earmarks actually make democracy more efficient rather than less.