Wasteland is best for iron, but i just hate the eerie sounds, wouldnt mind seeing it dissapear either
The wasteland, besides offering a variety of good looting opportunities and as you already pointed out an excellent source of scrap metal, serves another purpose – Being a distinct area with unique dangers to face. So I'd say no, that one should definitely stay.
Plains was just plain boring. Nothing special there you couldn't get elsewhere (and usually in larger amounts too, like coal mentioned by LuckyStar. There's way more coal PLUS oil PLUS fertilizer in the burnt available). No biome specific enemies, no unique POIs. Just a lot of running and maybe a little higher spawn rates for stags.
I guess in PvP it was nice for visibility of human enemies. There's still the desert for that now.
In PvE you could achieve more than enough visibility around a well placed horde base anywhere. Just a matter of chopping down some trees. The spawn-in distance of Zs isn't that far that you need kilometers of clear sight.
I actually prefer not seeing them pop into existence (That awkward pop-in and standing up animation...blech.).
(...) Shame they keep doing away with some of the older features.
I would have preferred an overhaul to the biome and giving it more unique properties to add to the variety of biomes. Variety is good, agree on that point and agree this direction is a bit of a shame. But of the many features and content being cut, because it's the easier way for the devs to go, this is one I'm the least sad about.