I'm kind of curious about trade in particular, because it seems to come up in threads for this game a lot and the consensus seems to be to keep it as is but automate as much as possible (or at least not break existing trade routes so often).
Why? Not why it should be automated (if it's like EU: Rome, it's a micro mess), but why bother having a trading system at all, or at least one that the player needs to directly control?
You get the ability to get more money than if the AI handled it off screen, I guess, but players are swimming in money anyways in every single Paradox game, because that's how the game progression works.
You can also stack bonuses/modifiers/enable troop types, but the first 2 are also something that there's way too much of in every Paradox game, and the 3rd really should be locked behind something else.
So why have a hands on trade system with these resources? From Paradox's point of view, it's a great time sink to keep you clicking and doing something in the game to get your payoff, but from your player's perspective, what's the point besides getting the payoff?
How would it take away from the game if it was something that you could look up if interested and indirectly influence like in Total War games (I blockade this province/exports halted/enemy loses money/resources) but otherwise you set something like a trading tax that increased or decreased your overall trade income, or any kind of system that didn't have you setting up individual trade goods with individual provinces?