Other than VoiceMeeter, there isn't any way to capture *only* game audio in Windows with your sound card; what you're asking for is simply not possible.
When (Windows) software outputs audio; outputs through an API to a sound device, the only one being your sound card.
VoiceMeeter creates a virtual sound device to allow a piece of software to output to that virtual sound device, so that another piece of software can record from it and capture only that software's audio. It isn't a workaround, its the only solution other than just buying a separate sound card or switching an operating system that has an audio backend that supports what you need (e.g. Linux & Pulseaudio/JACK).
If you do go and buy a separate sound card; you can use Windows' audio mixer to specify which programs output to what, so you can make your movies' sound output go out of the secondary card while the game audio is being output to and recorded from the primary sound card. You'll have to daisy-chain the outputs of the sound cards to the same set of speakers/headphones if you want to hear both at the same time though, and in my opinion that's more of a workaround than any software-based solution is.