If your game has "unique" feature it only means you didn't do your homework of finding dozens of other games that already did it before you
Why would they play it if there is nothing unique? Well, they might not know it because they haven't played enough games yet
For example, about the whole beaten up to death "program your robot to fight" genre. Do we really need another game of this type? Aren't these world wide championships of programming your virtual robot and kill each other enough? Yes, there is still a point of making these, you would be surprised how many people never ever heard about that genre! There are even people who might think that programmable robots are "unique", really!
The assumption that all people have all the knowledge is incorrect. Heck, I even stumble regularly upon game designers who don't know all genres and standard solutions to standard problems, imagine how low mechanics/genres recognition must be among regular gamers...
Anyway, instead of "twist" or "unique" I would use the word "focus". What is your game about, and much more importantly, what is it not about (exclusion is a more powerful defining factor). What will be your design goal, what you strive for the most, what your don't want to include and what are you ready to sacrifice.
Example "focus" or "core design decisions" from one of my games:
* fast paced and low time consuming
This game was designed for people who don't have much time. The micromanagement was cut to minimum. About 5-15 minutes a day will be enough for this game.
* lots of players interaction
You won't play alone. There are plenty of possibilities to interact with others. Not only solo attacks, but trade agreements, exchange of gifts, tributes, vassals system and factions allegiance will force even the shiest person to play with others.
* new players are valuable for everyone
Have you ever played a MMOG where at the beginning no one bothers or cares about you? That won't happen in this game. From the very beginning you will be flooded with offers from factions and sovereigns.
* free to play
You can play this MMOG for free as long as you want.
What's important is to not analyse if in terms of good/bad. This above excludes people who have tons of time to play and love to micronanage stuff all day, in exchange those who hate it and have no time will enjoy it more. It is not "good" or "best" decision. Completely opposite decision probably could be equally good, maybe even better. It's not important. Important thing is that when you decide to focus on something it makes your design decisions much more conscious (when you collect players suggestions you would look at the list and exclude all "I'm bored, I clicked for 30 mins and now have nothing more to do!" - it is not a game for this player, discard it; next another asked for better communication feature, interaction is second on the focus list you put that feature on top of the ToDo list, etc, ect).
In short, I think it is not important what you twist (focus) is as long as you stick to it till the end and don't try to make the game appeal to everyone and his dog.
