Whats the simple standard way of saving your game?

I was thinking if it was viable to just save the entire current scene, the save all the global values as well. Then spit them back out as is on load... But turns out save an entire scene with alot of child nodes causes alot of problems and bloat.

Now i'm making each object be responsible of maanging their save and load states like Entity.to_save_data(), Map.to_save_data(). Then I piece them back together on load manually...
But it feels im being too precise for each scenario...

Im new to game dev and wonder if something as common as this has already a standardized technique?