I tend to think of self-interest being equivalent to selfishness. Your point makes me wonder if self-interest is not equivalent to selfishness, at least to Economists.
Too many people seem to approach economy as an ideology rather than a complex system in which a given approach produces good results here and bad results there, and everything should be subject to optimization and careful design.
Few of these people have any decision-making authority. This mass ignorance of economics does occasionally bubble up on the policy side. But it is generally, at least in the United States, contained by more knowledgeable (and influential) parties.
They believe that if everyone acts selfishly, the outcome is still pretty darn good (but of course could be improved if nobody committed crimes or something)
Ideologies are mind poison.