Dominion as a Featured Game Mode
Definitely Not Dominion is a slap in the face to Dominion veterans. It's worse at capturing the feel of Dominion than Ascension is, and it doesn't feel all that fun to play (in my opinion).
I've largely quit LoL due to the removal of Dominion. Perhaps I'll get back some day, perhaps not. Dominion as a Featured Game Mode would have me play the game once in a while, at least. It is, in my opinion, much better than Definitely Not Dominion.
My suggestion: Keep Definitely Not Dominion for those who like it, but add Dominion to the queue as well. This way, Dominion veterans will be slightly happier (although likely still bitter that they can only play their favorite game mode once in a while), and people who like Definitely Not Dominion (not sure how many there are, I've seen maybe one or two that I know that liked it) will also be happy.
Also, when you're add it, add URF Dominion as a Featured Game Mode, it's a blast, I've played hundreds of custom URF Dominion games and it's some of the best times I've had playing LoL. Maybe experiment with URF Ascension and URF Definitely Not Dominion as well? Perhaps URF would make Definitely Not Dominion fun, who knows?