What if the actual conclusion is that it just doesn't matter. Growth is driven by other factors, like when a brilliant but insufferable physicist moves back home to be close to his mother [2], and is a function of individual, private firms performing functions of the economy more efficiently than existing incumbents. Tax policy follows as a consequence, and can go in either direction: either the newly-rich individuals think "Oh well, I've got plenty of money to spare, I can afford to burn some to ensure the people around me live decent lives", or they think "I want to keep more of this money to myself so I can decide how to allocate it." Regardless, wealth brings power, and so they have the ability to shape local government policy based on their particular worldview.
If this is correct, tax policy is a huge distraction, and if governments really want to jump-start growth they should be funding basic research, ensuring that the results are public (to their citizens, at least), and encouraging bright young people from across the world to immigrate to their jurisdictions.
[1] https://www.cbpp.org/research/state-budget-and-tax/kansas-pr...