Realize you are considering completely altering the hydrology that has historically served as the cradle of humanity's longest-lived civilizations. This project would touch huge population centers, many different cultures that speak different languages. What happens when people that have lived in costal communities for generations suddenly find themselves landlocked?
There's a reason this was an undertaking contemplated in the time period that it was. Herman Sörgel could propose this and simply not care what the consequences would be for the people that were already present. The Superior Race simply needed more Lebensraum, to hell with the inferior races.
One man's sclerosis is another man's stability. This is not hyper-conservation Western mindset, this is living in a world where one remote political power can not radically alter the living conditions for millions of people that are not represented in that power.
As I said, there would have to be careful study and consideration of the effects, and in all likelihood, it would fail, probably for the reasons you cite.
However, I suspect the modern knee-jerk reaction would be to reject these sorts of ideas out-of-hand, not because of infeasibility, but because of the "preserve at all costs" mentality that has taken hold among many, and then to look for ways to justify the rejection.
The will of industry has such a strong influence on political outcomes that it seems rational (though perhaps unfortunate) for people to oppose big projects as early as possible.
Also once built and the sea drained, the persons in charge of the dam wield immense power over those who move in and inhabit the new lands revealed. If they see fit, or someone captures the dam, they can hold to ransom all the people living in the new periphery of the Mediterranean Sea.
There's a reason this was an undertaking contemplated in the time period that it was. Herman Sörgel could propose this and simply not care what the consequences would be for the people that were already present. The Superior Race simply needed more Lebensraum, to hell with the inferior races.
One man's sclerosis is another man's stability. This is not hyper-conservation Western mindset, this is living in a world where one remote political power can not radically alter the living conditions for millions of people that are not represented in that power.