In the middle ages the nobility were effectively the government (and the church provided checks and balances, kind of) as well as the investor class. In addition to financing productive capacity they also did all the administrative things governments do. Obviously administrative bloat ebbed and flowed over time. Today we have both government investment in capital project (e.g. a road, or a bus terminal) and private investment in capital projects (a new factory or whatever). Both groups can get very rent-seeky and non-productive if left alone with no reason to not do those things. It's really hard to make generalizations that are more accurate than not.
I think comparison to the pre-industrial world is more effective for understanding that time than it is for drawing conclusions about our own time. All the details are so different you really need to squint to make things line up and when you're talking about big things like macro-economics it's the fine tuning and details that make all the difference.