The thing isn’t that a strong combat navy isn’t valuable, it is that (outside some specific circumstances) those resources can pretty much always be better invested elsewhere until you have broken the game open. Early game, the force limit and sailors are a much greater long term benefit when invested in light ships for the vast majority of tags. A small combat fleet is also not very useful early game, you generally need to go all in to reliably beat other people at sea while your lights can stomp weak nations.
The vast majority of wars can be won on land only while many wars don’t get any appreciable benefit from a navy. In addition, at peace time heavies are just a drag on your economy (even if mothballed) while your army can suppress rebels, earn money as Condottieri, or convert money into manpower by drilling. And even in situations a navy should be a huge factor, you can quite often just rely on the AI to screw up. I have crossed the Bosporus to kill the Ottomans while having no navy many times (especially once you get forced march). And for invading island powers like Britain, you don’t need to win the naval war, you just need buy enough time, which light ships can generally do (at a cost, but less than building a world class combat navy)
Late game I always have a doom stack or two of heavies as a QOL thing because I don’t care about money anymore.
My most valuable war navy ever has been a single cog that trapped something like 80k Ottoman troops on Hormuz for the entire duration of the war: sapping manpower from attrition, taking a big chunk of their income, and using up their force limit so that instead of being greatly outnumbered I could just stomp them. I have also tied down thousands of enemy troops by having a transport constant dock and undock, the AI would try to cross the straight when the ship was docked, but have to change their mind when it undocked, then it docked again and they decided to cross the straight only for it to undock...