They couldn't effectively police borders, so they didn't. Technology and population density influences the way the state works and whether they could do borders as they existed in the 20th century and exist in the 21st century.
The argument isn't against technology, it is saying borders as they are understood here are a relatively recent technology relying on other technologies
They’d kick you out and burn down your house or kill you for being an invader?
That is a complete anachronism, unless you actually were an invader. Have you actually researched this or are you just taking your assumptions and trying to apply them to history?
Presumably even though there were no border controls, they would kill you if you returned.
Honestly, I’m not sure what the fixation with a guy in a booth is about. Whether you get denied entry and they throw you out, or if they exile or ostracize you, what’s the difference?
Honestly, it seems the same. If a bar doesn’t want Jews in it and the bartender asks everyone if they’re Jewish or a bouncer at the door feels like a distinction without a difference.
There’s no additional liberty, the people who own the bar set the rules.