I want to speculate and discuss the game's upcoming features, they release dev diaries every Thursday.
https://forum.paradoxplaza.com/forum/developer-diary/victoria-3-dev-diary-3-buildings.1478868/
Last week they talked about buildings. Based on the screenies, I'm making this guess on their design. Pop groups accumulate "investments" (aka capital) through the dividends made on profitable private farms, mines, and factories. My guess is that the player will have access to those investment pools in order to fund more industry within their borders and internationally. Workers make products at a factory. Those are sold and workers and investors make a wage that they use to buy things. If there's a profit because income exceeded expected wages, then that money goes into the factories savings. Once savings reach a certain point, investors are given the rest, turning that profit into capital. The player controls all capital, state and private, owned by people in their country. What this may also mean, is that if a planned economy elimimates landlords and capitalists, it sends any dividends straight to your treasury. I'm sure this will have an efficiency penalty, but whatever, the soviets werent the best investors in the world. This might also mean you could mod in market socialist economies that divide wages equally between the employees, so the player has to rely on just taxes to accumulate capital.
Either way, I'm really excited to see what else they're changing about the game
i played a bunch of vicky 2 and also followed the development of a bunch of mods that tried to improve the economic mechanics of it (which were utterly busted at launch and never came quite right). one did the standard big-strategy-game-balance-mod thing of pulling a bunch of levers really hard at once, and then when that messed up things even worse, pulled a bunch more levers to try and right it, and so on until you got a hulking monstrosity bearing no more than a passing resemblance to the original. a second one tried to take a bigger-picture look, and have a consistent overarching strategy for remodeling the underlying economic system of the game. i cant remember the specifics, and i dont think the guy was a leftist, but i remember he ended up coming to the conclusion that there was a fundamental and unfixable flaw to the way the game modeled commodities entering and leaving circulation. i had zero economic understanding at the time so i cant comment if he was right or not, but given that the economic model really underpins everything else in the vicky games, i really hope they manage to do a better job with it this time