Sometimes it can ben walled, sometimes you have to wall half of the map. Yes, I understand you have to adapt to your map but the map has to be fair for both players aswell and sometimes your oponent’s map is wallable when yours isn’t. Furthermore, If you pick a defensive civ and the map is open you have a big dissadvantage from the start so it has a multiplied negative effect on your strategy.
I don’t care if arabia is open or close, I can play both but I think it has to be one option or the other. It’s like if in arena sometimes you start with walls and your oponent not. It just ruins the whole game.