Why do Great White Sharks not survive in captivity?
Most of the reasons why Great Whites are hard to keep in captivity are actually quite practical in nature:


Great White Sharks are expensive to keep because they eat a lot of food; their tanks need continuous re-stocking;
They refuse to be fed by humans, leading them to die of starvation. They do not seem to accept dead small fish for food;
The correct saline balance seems very important and difficult to maintain;
Logistics are difficult; they have to be safely captured in the wild, transported to a tank and that all the while keeping them in appropriate living water;
Due to their size and aggressive nature, great whites are hard to handle;
As you said already in your post; they are open water fish and cannot be confined. Sharks can swim hundreds of kilometers within a matter of days. This exercise and freedom may be essential to their well-being. A small 4-feet 'Great' White was kept alive for 6 months in a 1-million gallon tank. And even that was hardly enough;
They seem to get depressed in captivity. Great White Sharks that are kept within tanks have been known to head butt their noses into the glass walls and lose their appetites. It has also been noted that they get increasingly aggressive in their depressed state.


Sources
- IFL Sciece
- Science Alert
- Shark Bookings