As the server host guy I wanted to know if you had some ideas to stop a server from dying by changing the servers goal and not by modding the server ( Create Mod, ... ).
I think the real question is whether those people are playing Minecraft at all after 2 weeks. Some people only play a little bit then put the game down until the next update. If thats the case then there's not really a point in starting a server. If they are still playing Minecraft then ask them what they're doing that makes it more compelling. I sympathize with your struggle, my friend group went through the same cycle for about a year, server 3 was about 6 months ago. Sometimes people just aren't into Minecraft as much as you are.