It’s gonna depend on the terrain you hunt in on how effective they are. In my area they are great for going downhill but the ride back out sucks more energy out of you compared to walking. Packing an animal out is also very challenging, if you hunt in flat terrain areas then it might be doable but not in the mountains of Idaho.
Used one for years, bow lashed to pack when trolling for bulls, no trailer. Modified Burley kids trailer used to haul them out. We hunt gated roads in TMA’s.
I hunt gated roads with a mountain bike. Bow or rifle strapped to Exo K4 pack. For me, 40-50 lbs is very doable for packing meat while riding, much more gets too heavy and dangerous for any ruts or bumps in the road. If you ride downhill to find elk, you’ll likely have to push your bike out with a full load of meat. I prefer to ride uphill going in and cruise out at the end of the day when tired.
Hardtail 1x10 speed 29er with puncture resistant innertubes. Gun strapped to Exo K3 4800 pack while riding in/out. Adapter mounted to seat post to accept a 1" metal tube conected to game cart that seconds as a trailer. I mostly hike in, unless there is lots of road to cover between truck and hunting grounds. The bike and trailer stay locked in the truck until needed.
If you want to hunt off of a mountain bike. It helps to be a mountain biker. If you think you will just go buy a bike and go hunting, your ass will not like you. They do take work, but the style works extremely well for me.
I have pulled 15-20 elk out of the mountains of north idaho with this set up. But i am a mountain biker.
I have had the best luck behind gates.