I'm 28 (not old at all, I'm just hitting my prime, b****) and this games target audience should be the DMC fans. The fact that it's not is the issue.
If they want to reach a new audience, fine, launch a spin-off in the same universe with a different cast of characters or a new IP in the same Genre. Don't replace the wheel with a rock and expect your fans to keep racing!
It's like Hoobastank going pure acoustic just because they had a hit song that was acoustic. They sold their fans out to try and make a bigger buck. Pretty sure Linkin Park did the same thing.
Then you have bands enjoying major success by maintaining customer loyalty. Word of mouth and longevity go a long way to accumulating sales. Customer loyalty is often ignored yet is a very sound strategy.