I had access to a quad for the first time this year. I use it to get to the spot where I start walking, and will sometimes go back to it to help with retrieval. (There are ATV only trails that are sometimes an easier drag than the nearest road.)
I've done without for years, and still do better on foot. Use the other hunters to your advantage, and just be aware of the temperature/distance/steepness. If it's cold out, damn near any drag is fine; just take your time. There are also game carts and tow ropes and even splitting a deer in half and packing it.
There are cool places that I won't hunt without a motor for retrieval or friends, though. Some stuff is just too steep/gnarly to not put me into the ICU. But, there's plenty of hope for a guy on foot. Just know your limits, which it sounds like you do.