So far as rads go, Chernobyl is a good example to look at, five or so years isn't going to do much for radioactive decay,
Chernobyl is a great example of how radioactive particles settle into the soil and the most dangerous materials decay quickly as the area is regularly travelled through but you're warned not to dig or kick up dust.
I can understand mutations, like on the behemoths for example, having denser bones and possible thickened skin and what not
So, your actual issue is that the Zs don't look like they should be able to break the blocks, if they all looked like the behemoth, you'd be fine with it?
Well yeah, they could have artists do all sorts of special blocks that could be sat around like cooking pots, but then those artists would need to be paid, and every one of them is going to come with a performance cost.
I have noticed the game has greatly improved on voxel loading, and I personally have no issues driving at full speed across the map
One of the things they did that helped with that was reducing the number of voxels in the world. There are approximately 16 billion voxels in the world, most of them being non interactable air blocks, and that's after reducing the depth of the ground. Every interactable item in the game comes with a performance cost.
So far as traps, yeah, they are kind of just nice bells and whistles, but a variety allows people to make up their defenses in unique and different ways.
I get it, more graphical variation, everyone wants more, and there can never be enough, but we're back to paying the artists and every interactable thing coming with a performance cost. They're not going to prioritize too many bells and whistles until after the game goes gold.
There are of course the dart traps, but so far as I can tell they aren't terribly effective
They're more effective when combined with electric fences and more ammo efficient when set on a trigger.
Or a floor trap which launches zeds away from the base
Pretty much exactly what the sledgehammer turret already does.
wouldn't mind seeing a host of new zeds
There are mods out there that do just this, and again, I don't expect much expansion of the bells and whistles in vanilla until after the game goes gold. They have too many issues to solve before then.