How was Alfred Wegner's theory on continental drift wrong?

It lacked a convincing mechanism seeing, at the time, discovering sea floor spreading was beyond the means of the available technology. He also cited one or two dodgy details of no particular significance as being somehow supportive. One of these was the presence of the Mediterranean Sea to the east of the Atlantic and the Caribbean to the west, and this supposed symmetry was meant to somehow or other be meaningful. Then again, most of the evidence he presented was very strong.