Ok, I need help. I have seen this logic various times and I don't see the distinction.
First you do realize that it will take time to get money. That when they say income they tend to talk about gross income, which is what you make before subtracting what you are spending? So unless you are not spending anything you will quite possibly be forced to watch the game for years on speed 5 to get enough gold to still do/gain nothing?
So can someone help me in understanding how we are no longer sitting and waiting for a different colors thingy to grow so we can click a button?
It's actually easy to understand, the big difference between a wealth (money) cost and a monarch cost is that
I AS THE PLAYER can influence it.
For example with the new system I can decide to get inventions as a priority, meaning every 4 month equals one new invention. That decision will cost me troops, buildings (marketplace etc.) and other stuff, but a couple of inventions directly on game start could have huge impact on the game (for example the -aggression or -tyranny inventions). On the other side I can decide to spend all my money for new armys (while falling behind on inventions) to annex a neighbor "faster" -> getting more money or even enough money in the peace deal to speed up inventions/buildings etc.
Basically combining more player decisions to money or manpower are universally great because it creates a real choice. Only issue with that usually is multiplayer because it means people can use unintended huge impact choices (like only getting inventions, or only building armys to steamroll other players, etc.). My guess since release is that the decision for 4 different monarch powers was mainly for multiplayer.
If it is still not obvious how that is different from the current system:
Check military power. I as player can't really influence it because it is mostly rng how much I get (rule/heir/senators). Paradox will change that to a pure "every 20 years you get another tradition" and honestly it functions exactly 1:1 the same as it is now. The only difference is that I don't have to try to elect some idiot military commander to build a road instead of getting my military tradition. Especially because building roads without money but with military power seems wrong in itself. Similar with civic power, its just a horrible design to force an rng based gain the player can't influence. So if rng is good you can move a slave every month currently, if rng is great you can move 2 slaves every month and if rng hits you, you can move one slave every 5 month... -> I have no way to influence that. With a money cost that would be a great system, because I could always decide if I want to spend 100 gold (for example) to move a slave or not, etc.
Basically every decision in imperator currently is locked in the mentioned way above -> You are forced to rely purely on rng, can't decide anything and are basically forced to watch these powers going up to do one decision. On top of that you mostly don't even have a decision, for example currently a player spending civic power on anything else than inventions is actually hurting himself an that is at least in my opinion a horrible game design especially if it is the only design.