But by the argument that people balance themselves out you can just throw any balancing over board.
No. Only the balancing players do not like. This is what is happening by the way.
Players might select two ways of balancing: internal self regulation and external self regulation.
Internal self regulation: this is the one devs went for as it demands a high level of interaction between players.
No civ starts powerful enough to prevail over all the other civs. This means that the group of players can enforce any code of conduct they see fit by punishing any misbehaviour.
This is an active approach, players keep a watch on each other and crossings of a line is met by a collective response (involving all or some of the other players) to put the misbehaving player back in line.
It is intense, players must be involved and committed. They must keep an eye on the board to notice any dodgy behaviour. Players' plans are dictated by the board.
External self regulation: house rules, flavour mods etc
This is the one players wish for. The exclusion of any misbehaviour is guaranteed by an external rule that players had agreed on.
It is a passive approach. It released players from watching one over the other as the rules are not enforced internally.
This gives different outcomes.
A civ 6 game might last six hours. For the sake of the balance of power, a group must end the game with as many players as it started with.
By the 3rd hour, a player who is abusive might have taken an advantage over
a neighbouring player.
When the player is aggressed, depending on the regulation, the outcome is different.
In an internal regulation, the victim puts in the tray the possibility he might leave if the abuse is too violent.
If other players try to double cross him too harshly, (the agression serves everyone except the victim as it makes one competitor weaker), the player can threaten to leave (then harming the balance of power)
The victim must be restored in a acceptable state of power.
One example of external regulation is the house rule "no quitter" Players agree that no one quits no matter what. They do not want wto work to achieve that necessary condition internally so they outsource the enforcement of it.
A player might manage to abuse the other house rules and get an advantage early.
This time, though, the victim is left with no bargaining chip. Once he is put out of the race, he must endure the seven remaining hours for the sake of a rule that do not serve him. He cant bargain any restoration in power and the other players' main interest falls down to keep him in the game minimally.