But wasn't LoS mostly flat for its battles too? I can't actually recall much times when the terrain mattered in combat. No different levels of heights, no tight corridors where weapons could clash, environments that would deliberately change how you could approach an enemy, etc. They just covered the flatness up better than LoI and CoD, but for the most part, they were all very flat environments. Sure they had slopes and the places didn't seem square, but that detail was superficial and didn't change combat.
Of course, it did have like one or two instances, like the sword masters and the pools of water, but it was as rare if rarer than platforming in LoI.