If you ask me, right now the game has a good amount of content. Problem is, the content is just not being used for much or very well, and as more stuff is being added, it too is not being used very well (and old stuff is being forgotten even more).
An example is leather. Right now the game has leather. Whether it's from a rabbit or a god damn mammoth all leather is equal. In reality, these two animals would produce vastly different leather. Rabbit hides tend to be soft and supple, while something like an Elephant (close enough to a mammoth) produces leather that is thick, durable and hard to work with.
If I made armor from an elephants leather (or mammoths), I'd expect it to be tough, heavy and provide me with a ton of protection, but it'd also restrict my movement. In comparison, armor made from a rabbits leather would give me inferior protection and wouldn't be nearly as tough, but it wouldn't restrict my movement.
Each animal in the game (and in real life) produces different kinds of leather with different uses and properties. You made it so cooked food changes based on the ingredients used, this system could be expanded to encompass more things in the game, like leather.
Another example is the many types of trees, bushes and stone in the game. Not all of these are equal.
Naturally all woods and stones have different properties. Some are harder, some softer and so on. But I can't see these properties having much use in the game currently because there is little in the game to make use of it (maybe bows made from different woods could have different properties).
But for individual things lets take a few examples.
Alder Trees - Wood is used for smoking fish, bark contains an antiinflamatory that is good against insect bites, another part of the bark can be put in a pipe and smoked, it can also be used to make red and yellow dyes.
Birch Tree - Can be used to make oil which is used to treat leather and prevent it from cracking, birch tar is waterproof and makes decent glue, that bark can be used to make bowls, canoes and even wigwams (tents).
Elm Tree - Can be used to make a medicine to help relieve pain, the wood was a favourite for making bows and a variety of other tools, parts of it can also be used for cooking and eaten.
Poplar Tree - The wood was often used to make shields (was as tough as oak but significantly lighter), is used to make paper, is a good wood if you need to light a fire by hand and the logs are used to grow shiitake mushrooms.
Arrowwood Bush - As the name implies, it was good for making arrows. The fruit could be made into jam and the bark had medicinal properties (stops muscle spasms).
Bittersweet Nightshade Bush - It's poisonous, eating parts of it will make you vomit (take an injury but lose current FEPs or something). The stems are good for treating skin problems and other parts of it are good at preventing the growth of bacteria.
Dog Rose Bush - The fruit can be used to make tea, syrup, marmalade and even wine.
Dolomite - Can be used as a flux in the smelting or iron and steel (helps to purge metal of unwanted chemicals and to separate slag from metal), it can be added to soil to alter it's PH level for better plant growth and it's a source of calcium and magnesium for animal feed.
Feldspar - Used in making ceramics (use to be in legacy, is it in the game now?), glass and even as a filler for paint.
Flint - Obviously to make fires, also used for arrow heads and sharp stone tools. Was used as a gemstone and although the game might never get them it was even used in flintlock guns (hence the name).
Even smaller content like forageables could have more uses.
Yarrow for example in real life is used because it attracts good insects. Instead of having to run around the world looking for ladybirds, you could plant a bunch of Yarrow and have it attract them. Maybe if you plant enough you can attract things like hoverflies which could be some kind of new, rare curio.
This is just random examples. You could go through every tree, bush, stone type and forageable in the game and probably find several uses for it of which many could be implemented in the game.
Kingdoms are another feature that is criminally underused. When I first saw them I thought we'd finally be getting some Civilization tech trees and more progress. What we got was basically a bunch of stat bonuses.
We could have had some kind of end game content and long term goals with kingdoms. Researching and learning new technologies instead of just some endless quality grind. We could have been making new weapons, armor and tools instead of the same ones over and over to improve them slightly, new buildings and vehicles and so on. Kingdoms could have been so much more than a few stat bonuses for people inside of it and I still don't know why this isn't a long term goal. Hell, if you wanted to force interactions between players, you could have made it so kingdoms could not unlock everything, so different kingdoms had access to different end game content, forcing them to either trade or fight and pillage these things they wanted.
I could go on for days and days with this stuff. But I think you get the idea. A lot of the content currently in the game has very few uses and most of it could be worked to have many more uses. Would be nice to see content with more depth instead of just piles and piles of content with little depth.