I see what happened. Instead of having the triangle slide between wealth, research and manufacturing, they gave us deficit spending. Production does NOT come to a complete halt like it does in vanilla GC3, instead it continues at base production levels. Haven't figured out yet if the factories shut down and population keeps working, or if population goes on strike while the colony capital continues production. Either way, you're not frozen - only penalized - if you're balance is negative. You can still dig your way out of debt with proper planning. 

I approve of the change, but I still miss the production triangle OR the tax rate slider.

Thats it in a nutshell. The functionality of the triangle has been replaced with leader citizens which fill the same role of on fly civ wide adjustments, but they can be allocated to even more forms of production than before (as you unlock more techs) and you have other types for bigger boosts on top of that from other specialist citizens. But it's gated now so it's flexibility and intensity grows as the game goes on rather than being fully unlocked at the start.

Indeed. The leader does the same thing except,much more flexible.