Dominion has a real uphill battle because it plays differently from every other permanent map. To win in SR you push lanes and kill towers. Same deal in TT and ARAM.
In Dominion, you can push lanes and cap towers, but that is super un-fun. That's because it makes you lose the game without much happening. The lane minions really don't help you capture the tower, and being in lane makes it super easy for the opponent to counter defend your movement. Meanwhile, the winning team merely has to defend while the losing team has to be aggressive, which is the reverse of every other game mode.
The way you actually win in Dominion is to control the jungle and make good map rotations. One of the things I see people complain most about Dominion is back-capping. This is a strategy that doesn't exist in other game modes, but is core to how Dominion works. The winning team has more points, thus has more objectives to defend, which gives the losing team an advantage to pressuring them.
I believe that Dominion has a major issue with attracting and keeping new players because of how different it is.
Riot needs to shake up the mode a little bit and put some serious thought into secondary objectives on the map. They need to push players towards the middle of the map, not towards the outside lanes like the minions currently do. There's a really great core gameplay in Dominion, but Riot really needs to spend time iterating on the map to make it appeal to more people.
I would love it if Rioters would discuss ideas with us. They're always so silent responding to ideas for Dominion.