I don’t know if they offered nothing. But European monarchism is a government structure situated in the past. It arose out of the material conditions and culture of a certain place and time, that no longer exist. Further, it’s ideological justification, the Mandate of Heaven, would be strongly contested by contemporary people.

So I don’t think it’s rational to transpose the historical benefits or flaws (if it’s even possible to disentangle the causal relationship between government structure and societal outcomes) into the political discourse and assume they would remain the same. One salient massive societal change has been the de-mystification of the aristocracy due to increased transparency. Instead of reverence, commoners view these people with contempt or even pity.

Speaking generally, I think way too much emphasis is being placed on the importance of government structure on outcomes. I understand why programmer types would be drawn to this analysis. But there are more salient dimensions: societal trust, peoples sense of stake in outcomes, the integrity of institutions, and material conditions.