Taxes promote inactivity. It's why you've seen the player base dive off a cliff. If you're not making any income to get more cards what is the point and they leave. 3rd edition of course will bring some love and honestly you can buy SIM for next to nothing to grow your city but most people don't do that.
Taxes promote behaviour that minimises such taxes - unless the individual can do nothing about them, and then they feel like part of the rules rather than part of the game.
The suggestion is not so much about taxes, although that is the mechanism, but to introduce another level of feedback that seems missing.
Yes, your suggestion is correct, all users can play the same big-city game, but that in itself is one of the consequences: that a game that has at least a handful of different strategies, that work at different levels, has become overwhelmed and dominated by a single strategy.
If this wasn't obvious before, it is now, so the suggestion is mainly to return to a diversity of cities - and a diversity of players.