My two cents in the matter:
The reason servers like Hypixel bring in a lot of players is not JUST because it's all mini-games that appeal to kids, but because of THE QUALITY of said games. Custom textures, good scripts, etc. If we are to make a good SMP, we need to stop getting so comfy with vanilla Minecraft, and start adding new elements, objects and decor that can't be found in vanilla--items and stories people are so lazy to even bother installing on their own that they feel forced to come to your server instead!.
The "YOU NEED US/OUR PRODUCT" catch always works best!
When you go to a store because you ran out of milk, you go there because you need it and you can't make milk at home because you don't have a cow (and if you're lucky to own one, it's probably miles away) The problem we have as a community is that we have spent the past few years trying to sell milk to farmers. Maybe give them some f*cking tech and I bet you'll get your cash?
TL;DR - If people already own vanilla minecraft with vanilla items, why the hell would they come to you? Offer things they can't replicate in singleplayer/realms/private-servers/or most servers. Offer them the hard work they don't wanna put in. It's a consumerist society y'all. (Make em' donate for ranks/power ups/etc (eventually that is)