The journalist was making a comparison between the economic effects of the Spanish flu at the end of WW1 and those of Covid19. And disinterested means impartial/not influenced by private feelings, not uninterested.
"However, there are some key differences, not least the fact that the Spanish flu disproportionately affected those of prime work age, whereas the coronavirus primarily kills the elderly. In the First World War outbreak there was thus a lasting impact on supply, with many families suffering the loss of the primary bread-winner.
This is quite unlikely to occur this time around. Not to put too fine a point on it, from an entirely disinterested economic perspective, the COVID-19 might even prove mildly beneficial in the long term by disproportionately culling elderly dependents."
If you read the entire article you might just get the idea he's talking about global economics, not wishing death on old people.