Basically "you can't give constructive criticism on something that basically doesn't exist." is not true, you know why? Because if this doesn't exist I wouldn't make a topic about it... games take years to create son.
then loving make a post about it once you have an actual viable idea with all the mechanics outlined and exactly what you want out of the game. make the loving post when you have a minimum viable product that gets your game's main idea across to people. it doesn't take years, it takes maybe a month or two, and once you show people you actually know what you're doing than they'll actually take your project loving seriously
dumbass its a robbery simulator
capture the flag is a robbery simulator. how is your 'project robbery' different from the vague loving superclass of actions that fall into the category of 'robbery'? how is your game different from jailbreak? how is it different from cops and robbers? what the hell is it? what do you do? how do you do it? why is there any reason anyone should care about your game?
these are all questions you haven't actually answered yet. you've just thrown this really vague abstraction of 'you rob a bank' which could mean anything from watching a video where people rob a bank, to robbing the bank from the perspective of a robber, from building the bank and designing it so it is robbery proof, to loving planning the entire heist. none of this at all is clear. you haven't clarified anything in your post besides saying you get to play as a cop or robber, and you haven't told anyone what you do.