Spring, summer, and fall differences are barely noticeable mechanically, with foragers being slightly affected by them. Winter feels just like something you have to wait out, or that you can ignore completely if you're not a farmer (considering now it's short, so u don't really need to hunt in those 5 days). And treeplanters get screwed for most of the year.
What can it be done to improve it?
I see two main options:
- Make seasons less important, focusing on the aesthetic aspect.
- Make seasons more realistic, and matter a lot more.
Seasons for beauty
Seasons don't necessarily have to introduce many new mechanics. They can simply give the game a nice new look that changes over time. The foliage colors of autumn, the snow and ice in winter, and lots of flowers in spring.
Gameplay wouldn't change much over the year, and people could just ignore it or enjoy the view.
The only "real" difference could be the snow and ice covering land and water in winter, which can be likable but doesn't change your everyday activities too much. Seasons could all last the same, maybe a month each. A new player spawning in winter would have the same experience as someone spawning in summer.
That would be a perfectly fine way to have seasons.
Seasons for gameplay
If seasons are supposed to be something to take into account, not just a pretty thing to look at, then they should be a lot more seasonal mechanics.
First of all, you'd have to decide if you want it to be more about realism, or more about "random fun stuff".
- If realism is a priority, then all seasons should last the same. Crops should be seasonal, animal breeding should be affected, things you can forage should change a lot more, and winter should become a challenging time you need to prepare for. I believe you tried this already by creating a shortage of things in winter: no crops, no tree seeds, and fewer animals around. Unfortunately this made winter boring, leading to it being only 4-5 days long to prevent people from quitting for its entire duration. In order to have a challenge, you need to be pushed to take a somewhat dangerous action in order to avoid a worse outcome. In your first announcement about season you mentioned temperature: by itself it wouldn't be enough, because the solution would just be never leave camp in winter, and maybe keep a fire up, which are not just not-fun things, but also so easy to do that they don't create a challenge. Temperature would work only if you are pushed to go outside anyway: the easiest thing to do would be adding some very valuable winter resource that pushes people to fight the cold to get it. Alternatively, but this would require some major changes, a real need for food and decay mechanics for fresh products, which would push you out of your villages during winter to hunt for fresh meat; hibernating animals should be found in cave systems, making hunting in winter more of a treasure hunt in caves than a random stroll around the woods. Maybe even some tracking system could be added, eventually. This wouldn't be necessarily fun, but it would be a challenge (kinda like wounds are, even though they are a very easy challenge after just a couple of days)
- If realism is not that important, then more "fantasy" things could be added. Many seasonal plants, including crops or trees/bushes that only grow in winter would keep farmers busy; season-themed animals and monsters (animated snowballs/snowman, walking flower-creatures in spring, leaf monsters in fall...) to make hunting more interesting all year long. Useful recipes made seasonal reagents (from above mentioned plants/animals but also from things we already have like snow or autumn leaves). Things like these would make seasons more important and more fun, without adding challenges.
In either case, it would be better than now.