I think this is a bit like the "Anna Karenina principle." To be a successful game, it needs to be great on many different facets, but one bad thing could turn the entire thing down.
Therefore I think it's wrong to focus on what's people want, because it can be very difficult to do, and different people want different things. I believe it's more likely to be successful if designers focus on what they want (or more accurately "envision"), while avoid pitfalls where people might not like. For example, if it's apparent that players no longer like grinding, it's probably a good idea to avoid making a grindy game. It does not guarantee success, but in an environment where people don't like grinding, making a grindy game is certainly a recipe for failure.
Therefore I think it's wrong to focus on what's people want, because it can be very difficult to do, and different people want different things. I believe it's more likely to be successful if designers focus on what they want (or more accurately "envision"), while avoid pitfalls where people might not like. For example, if it's apparent that players no longer like grinding, it's probably a good idea to avoid making a grindy game. It does not guarantee success, but in an environment where people don't like grinding, making a grindy game is certainly a recipe for failure.