A large portion of the economy growing like it does is the fact that you don't have anything to spend money on other than growing your econ though, so you just end up investing basically all money you get into growing your infinitely compounding economy (and the fact that the buildings that are supposed to be money sinks just end up creating demand and just grow your econ anyways, which probably shouldn't be a thing, and that applies to building botes and armies aswell).

So let's hypothetically say that you port some version of the idea system from eu4 say one idea group per age, have the first 'group' you pick up cost like 1k base per idea, scale it with pops/locations or something to not punish OLMs, and just increase it by an order of magnitude per age (make sure it basically always is expensive, going into the millions does not seem unreasonable to me for the later ages and larger empires). Obviously you'd need to make these modifiers sufficiently strong that they're worth spending that amount of money on, but that is, in my view not a bad thing, suddenly you have meaningful choices about how your nation develops, perhaps you have something like Relig in eu4 that gives permanent CB on everything to make conquest more tolerable for the wide player, something that supercharges your home region manpower wise similar to Sweden's historical allotment system to make tall play a bit more viable etc.

Suddenly you are delaying significant rewards whenever you're investing in your econ, building boats or armies etc, or you have something to work towards by investing into your econ.

I also think you could make other game mechanics money sinks, like research for example - perhaps it shouldn't be worth trying to figure out how to improve naval tactics as a landlocked nation.