Campbell SMP is starting its second season and it feels like a fresh new world that still wants to last a long time. It is a semi vanilla style server but with extra world generation and cool upgrades so it does not feel boring.
You start off simple and then unlock better tools and armor by leveling up your skills. You cannot just jump straight into iron and diamond gear. It makes everything feel more earned and gives you a reason to keep playing.
The bosses are not easy at all. The Wither and Ender Dragon are harder so the fights feel more epic. There are also regular events so people always have something to do together.
The world has upgraded terrain and structures like better temples and ocean monuments which makes exploring way more fun. There are server side decoration blocks and Farmers Delight so bases and farms can look nicer without everyone needing mods.
Players run the community and vote on how things should be done so it really feels like a group project instead of just one owner deciding everything. There is proximity voice chat so you can talk to people nearby in game which makes it feel like a real town.
It is meant for adults who want a long term SMP and want to stick around for more than one season. If that is the kind of survival you like this server seems like a good place to join.

