I know nothing about coding or github, but an idea that I always thought would flesh out the mid-game would be quality. Just because I can conceptualize a crossbow doesn't mean I'd make one that's any good at the start
Cooking - at 0 skill your meals are bland, you waste time and materials, and because of the waste they aren't as nutritionally filling. These would be "Horrible (Meal name)." As I cook more, and specifically cook that recipe more, I would be less wasteful, it would be cooked properly, and I'd get faster at it
Electronics - Your first crafted electronic devices would be very wasteful, bulky, require frequent repairs, and impact the quality of whatever you're using them for
Survival Tools - Again efficiency. Your crappy smoking rack you threw together because you understand that smoking meat will preserve it sucks. It takes longer to preserve the meat, and sometimes fails to do so before the items expire. It wastes fuel too
Weapons - Poor weapons would be fragile unbalanced and less effective in damage
Armor - More encumbrance, more weight, more volume, less protection, less storage, etc
Etc
You could even turn this into a whole new sub system of crafting skills. You would gain theory from crafting or reading, and you'd gain practical from disassembling higher quality items or using poor quality items
Just a thought. I don't think things need to be gated to improve the skill systems. I think the skill system just needs to have more depth to it