I learned to hunt in the 80s with my dad door-knocking. Rural Kansas has changed a lot since then. Even in the 80s, the chance that the person behind the door owned or controlled the land you were going ask about was less than 100%. But today, that chance is almost nill. The owner often doesn't even live in the state and the person behind the door you knocked has no idea who farms it. A guy and some equipment show up once in a while. He does his thing, and he's gone.
It's more like phone-ringing than door-knocking these days. Permission can still be had, but it takes research and relationship building. Never forget that we are an intrusion, a distraction, a risk, etc.