As Intended_Pun said, realism itself doesn’t add much to a game, and you’re better off focusing on one (or a select few) core gimmick(s) to make your game unique, quality and achievable.
Realism doesn’t even fit the style of Roblox that much, Rthro or not. In my opinion, it can usually only be pulled off on Roblox if it’s through a ton of specific work on something like a showcase or a high quality, linear, story-based game like Roses. It is entirely possible to make good looking games that are fairly simple and unique. Jailbreak used smooth terrain and a simple and unique low-poly style – and it was even built/modelled by one of the best builders on Roblox, which says a lot about the value of not going the realism route.
As for features, you want to find something that makes your game your game and build on it, make it great and fun. You want something to market to your players, which is where your unique and defined features come in. Having too much features not only bloats your game, it creates a ton of work for you and can go way out of scope.
Even behemoth games like Jailbreak originally started out really simple: If you’re a prisoner: Escape jail, rob the single bank building in the map and don’t get caught. If you’re a cop: Stop prisoners from escaping, get them back in jail when they do, and stop them from robbing the bank. That was the core goal, and it was the focus of all of the other features – which there weren’t many of, since there were really only vehicles and weapons back then.
Also, another thing to remember is your target audience. I don’t know, and have never known, of a kid younger than 12 who cares about realism. AFAIK, they don’t care. Roleplaying is similar; while it may be appealing and popular, you must also remember that your audience are simpletons (it’s a pretty bad way of saying it, but that’s the truth). Compare Meep City to whatever your game is gonna be like – Meep City is successful because of roleplaying, but to me it seems like you are going for something that is way different. Not to say you shouldn’t take risks, but there are ones that seem worth it and others that don’t.
There is an advanced roleplaying niche on Roblox, but do remember they probably won’t be getting you the numbers you want.
Game design is a hecking nightmare!