Lots of these highly qualified researches are forced to leave science right now, the reasons all too often not being their qualification. There would be a large pool of good researchers to draw from for this.
How would each of those specialists retain currency in the field by just doing reviews?
Isn't that what the editor panels do more effectively today (of course farming out the detailed/specialist aspects to actual peer reviewers)?
„Currency“: Broad expertise, knowledge about methods and ideas are gathered by reading literature in-depth, which most scientists have little time for in modern science (hence the reluctance to engage in a long peer review process). Working as a paid reviewer for a few years can lead to a scientist who is informed very well about the state of the broader field and its various fallacies, and could move on from there. We have very few of those.
Editors: We wouldn’t have various discussions around peer review if the current system would be working satisfactorily well and nothing needs to change.