> My impression is that the vast majority of "savings" was never achieved by promised efficiency gains or elimination of pure waste, but instead simply by cutting projects, i.e. slashing some form of public service or benefit in order to save tax money. Which is obviously inferior.

That doesn’t seem inferior at all. There’s very little to be gained by doing everything the same but with less money; the only way to make an actual difference is to quit doing the stupid shit that’s expensive. That’s what 90% of the world means by efficiency, i.e. don’t do the things that don’t need done.