I have played extensivelly with RCRN, CoT, and use Realvision ENB. I have used ELFX. Now I just want a vanilla game with darker nights and dungeons without weather mods. I plan to continue with ELFX or RLO.

So for this game I want to have:

dark nights

dark dungeons

..without weather mods or mods created in 2012.

Any suggestions for what I need?

AFAIK, the most popular is:

http://skyrim.nexusmods.com/mods/12454/?tab=1&navtag=%2Fajax%2Fmoddescription%2F%3Fid%3D12454%26preview%3D&pUp=1 (doesn't require ENB, but made with it in mind, obviously)

But there's also (I haven't used these):

http://skyrim.nexusmods.com/mods/27960//?- also made with ENB in mind

http://skyrim.nexusmods.com/mods/11353//? and http://skyrim.nexusmods.com/mods/11356//?

http://skyrim.nexusmods.com/mods/3612//?

Also, http://skyrim.nexusmods.com/mods/24235/?tab=2&navtag=%2Fajax%2Fmodfiles%2F%3Fid%3D24235&pUp=1 is close to vanilla looks, with the perks of ENB, including darker nights. I know you said you didn't want an ENB, but this would allow you to easily tweak nights & interiors to taste, while still having a vanilla feel.