Because now Wikipedia editors are required to have the same expertise in each subject as academics who spend their careers in those subjects. I submit that model is clearly not sustainable, and quite different from not expecting them to expend intellectual effort.

Wikipedia is not a place for original research for exactly this reason. Once something has gone through peer review, and is published somewhere, then it can be used in Wikipedia. I think that's reasonable. Wikipedia editors are then relying on a particular subject's community of experts instead of having to be those experts themselves.

I think it's also important to note that this model is the same as any other encyclopedia.