We didn’t then either. The real issue is scale. What worked when the entire population of the human race was 100,000 doesn’t work when it’s 8,500,000,000.
You’re right that there are no wilds no, no one is getting 40 acres and a mule, and you can just inhabit a new area.
But let’s not forget that a lot of the stake a claim and defend with lethal force was literally colonialism. So many of those wilds were owned by other people, but the stronger guy with the bigger rock can kill him, take his land, take his wife.