The game in my head is a semi-open world story-driven action game including a multi-player feature integrated on single-player like Dark Souls. Its genre is a combination of RPG, FPS, TPS, and RTS
I'll be nice, and give you a genuine reply:
That doesn't sound very good.
There's this misconception gamers have that more is always better, but a combination of action, RPG, FPS, TPS, and RTS just
does not sound fun.
Everyone seems to have the idea, when they're young, of what I call "the Everything Game." It sounds awesome. But it's just not an idea that lends itself well to a good gameplay loop. It's too broad and it's virtually impossible to execute all those components equally well — and even if you do, not everyone is going to like all those genres.
Do you want to know what kind of ideas I
actually value, the kind I wish I thought up myself? Stuff like Untitled Goose Game. It's easy to see the appeal and the reason why Panic (the publisher) actually reached out to the House House (the developer) to offer to publish it, which is something that almost never happens. Those are the kinds of ideas you should try to have, creatively. Baba is You is another one. You hear that pitch — a puzzle game where the rules of the game world are manifested physically in the environment and are able to be interacted with to solve puzzles — and it's just like,
whoa. Those are the kinds of ideas both players and publishers actually want, not weird unfocused Everything Games. And, not coincidentally, they're actually ideas you can build a demo of as a solo dev or small team.
I'm not saying that to discourage you. If you have a passion to make games,
go for it. If you just have a passion for this specific idea, well...lots of people have passion for this specific idea, when they aren't very familiar with what makes games actually fun to play.