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.
In regards to defensive civs vs non / up until castle age, and to a degree until imperial age, even goths can play defensively.
Walling in itself can be a drawback unless it’s minimal walls vs. semi or full boom / arabia when trees are more condensed and easily walled is nice, but both sides should have a similar first 3 tree line generation for sure / I’d prefer the treelines to be closer for my own personal reasons but from the perspective of full walling it shouldn’t be easy so the tree lines should be further away for both sides.
The tree line generation could be limited in distance to the tc and random for each player within brackets of possible positions with a minimal and maximum distance from each other treeline to keep things from being fixed while retaining a degree of random generation
The map gen is one of the factors who determines your play style. There are many other factors as well. Picking your strategy accordingly using all factors is part of that makes this game so great. No match will be played equally. You have to adapt always.
Your civ pick matters more. Just pick one of the 4-5 viable civs and play only those.