I think "game breaking" is way overused when it comes to this game. Sometimes, someone rolls a perfect start, and they have a perfect map, and then they use the OP modes that just make their civ bigger... and then they declare it's "game breaking".
There is literally no civ that breaks the game, in every map, every option, and no OP game modes permitted.
"Yes, Ethiopia is game breaking if I have Highlands map, with Apocalypse mode, and Great Bath and Voidsingers."
"Yes, Portugal is game breaking on Archipelago map, with max city states, and Owls of Minerva"