I guess this might be an effective way to get someone into working out, but ultimately it's just a gimmick similar to those late-night products that generally don't do much.
I'm a bit of a fitness buff, I've been working out pretty my whole life. I guess the things that jump out at me that are off:
1. I wouldn't personally say 'we hate working out'. That to me is the wrong message. Working out is rewarding and worthwhile, for me it's something I look forward to every day. If you want to aim your messaging at people that feel that way, then say it that way - 'If you hate working out, this is for you!'. I'm not wild about that messaging either but at least it's not coming from the founders which to me is a big turnoff.
2. This is not a full body workout. There appears to be no leg resistance and/or emphasis on leg training. I would be careful in how you present this in your messaging.
3. I would position this as an intro to working out and partner with someone (if you can) like AthleanX.com which is are science based / physical trainer designed full body workouts. The reason I would try that is because you will likely have 2 outcomes of your users. Outcome 1 - they'll play it for a while, feel good about themselves and stop, or they'll maybe finish the full game experience, and stop. Outcome 2 is someone that really gets into this, sees some transformation of their upper body and wants to move on to a 'real full body workout' (which sorry this is not). That kind of partnership would be a win-win for both parties because it's a bit tough to jump right into a typical full body workout (esp. the AltheanX stuff which is really aimed at elite athletes), and having something like this as any easy onboarding process could be pretty cool. It would also be beneficial to have the expertise of a high-end, well designed full body workout help guide future workouts for your product. Right now, it really doesn't look like the movements, or punching is all that varied.
4. I also have a VIVE/VR setup and like others, I use that as part of my workout; in my case it's more a post-workout workout. I don't expect it to really develop muscles, or improve my cardio all that much, but it's a nice way to burn some extra calories and get some cool hand-eye coordination / dex training into your workout that is otherwise hard to come by (Space Pirate Trainer, Pistol Whip, Beat Saber for example).
Either way good luck, I do think the future of fitness is in some form of VR, AR + interaction/gaming.