No way you’re going to make as much electricity as with conventional hydro. Furthermore, you lose the ability to dispatch more or less electricity depending on

No way you’re going to make as much electricity as with conventional hydro. Furthermore, you lose the ability to dispatch more or less electricity depending on demand, which is increasingly important in grids with a lot of wind and solar. It may well be that the environmental costs of many dams aren’t worth it - and lots of dams produce very little or no hydroelectricity. But run of river hydro is not an easy substitute for those hydro plants that do produce significant energy.