thus leading to the rich get richer result.

Not 100% true. Both MIC war tax benefit and Eco tax benefit depend on the size of your SIM income and how many buildings you have. Many smaller cities will benefit far more from both, because the SIM they lose to taxes is much less and the reward for owning the buildings is flat — it does not scale. You would be better off having 2 MIC's in a city that gets 1000 daily SIM income than having 5 MIC's in a city that gets 10,000 SIM income.

With eco tax, same idea.