Terrain was removed to promote further/easier development, stone age man.
thats how it works with all features. the more you cut, the less you have to worry about. removing vehicles and their physics makes it easier to work with player physics. you can rewrite systems to make them easier to work with. i've seen so many cases where indie developers scrap their engine because it was all poorly patched together. but, of course, they remade it to be better than before by adding new features while keeping, yet improving, the original ones.
people are going to complain and justly so. thats what happens when you remove things people have gotten used to. the developers say "its going to increase update speed" but people have yet to see anything more than "official" add-ons. if people are going to be satisfied, they are going to want to see their old features back, or at least a way to compensate.
a vehicle physics update would be nice. if you've played my tdm, you see how stuffty tanks work with the bricks and how planes can fly through cubes, jeeps can drive through walls, and tanks get stuck on 1x height slopes. of course. a way to loop a "brick terrain" would be cool as well, that way even if we don't use the whole thing, the map doesn't just awkwardly end with steep cliffs or infinite space.
players would like to at least hear about features like this possibly being added in. it would be nice if we saw the "true power" of terrain/interiors being cut