A pork project is, by definition, good for the economy of the local area in which the money is spent, and at the same time is a net negative for the national economy.
The cumulative effect of thousands of pork projects is to make every local economy poorer than it otherwise would be. In Congresscritter Smith's district, the positive effect of the projects that Smith secures for his district (influx of money) tends to be outweighed by the negative effect of the projects that the other 434 congresscritters secured for their districts (outflux of money). The exception is when a congresscritter is particularly slick at scoring unearned freebies for his local economy, at the expense of the national economy.
Eisenhower didn't articulate the problem in these terms. If he had, Joe Schmoe would be closer to understanding (and using his vote to do something about) one of the worst aspects of our system of government. The president made a campaign promise to "fundamentally transform the United States of America," and pork-barrel politics is the aspect most in need of "fundamental transformation," but sadly, it has only been reinforced since 2008.
A local magazine surveyed dentists, asking "who, besides yourself, is the best dentist in our city?" By not allowing dentists to vote for themselves, the survey produced a much truer guide to where to get quality dental care. Similarly, a constitutional amendment that bars congresscritters from seeking to have money spent in their own districts would boost the overall effectiveness of government. Lockheed would finally be pressured to source its F-35 components from the most efficient suppliers, rather than from the most pork-ified network of suppliers.