This is your warning that there may be Re9 spoilers below. I don't think so, because much of what got me thinking was already in the trailer, but anyway. Warning.
Two things frequently come up when people complain about Leon's section in Raccoon City - the vegetation and the colors. And I just couldn't stop myself from saying my piece.
Why everything is so dull and muted in colors?
Because it's a dead city, duh. There's no inhabitants to give the houses a fresh coat of paint, to sweep the streets, wash the windows. So everything is gonna be covered in dust. And you know, can't really block the elements from doing their thing for over 30 years, so the sun, the wind, and the rain did bleach the color out of the city. So yeah, grays and subdued colors will be predominant. The zombies don't care either way. And any military or BSAA convoy rolling through there won't much be interested in the aesthetics.
Now about the plant life or the lack of it.
Many people bring up The Last of Us as to what they think RC should have looked like. You know, the lush, reclaimed-by-nature state. Which is fair enough! But. What do plants need to thrive, simplified? Sunlight, nutrients, water, oxygen, space, weather. The right kind in the right amounts.
Sunlight and oxygen, there is plenty.
Space - Most of RC shown is covered in concrete. Which is not an impossible issue for plants to overcome, but an existing one nonetheless. Additionally, the heat bombs probably sterilised the ground, delaying the return of flora in the immediate vicinity of the epicentre and the concrete would make it hard for seeds to get into the soil.
Water and nutrients - there is vegetation, the more the further outside we are. I think that is due to the chemical contamination of the soil and the groundwater from the hidden and not-so-hidden Umbrella facilities being blown sky-high. And no one thought to do a soil swap, so... Thoughest weeds win (and turn into monsters maybe). Speaking of, where the heck is the river? I haven't seen sign of it - could it have been diverted? Although that'd track with the contamination issue.
Weather - It's October. Autumn. Getting cold. Circulation stops, trees lose their leaves. The ones in the background seem pretty lush (while the ones in the city are pretty... dead), but based on the forest Leon drove through, most of them are probably conifers. There are dead leaves clinging onto some branches of trees in the city, so those had to have a crown not that long ago. (Though personally these trees still look like they are surviving, not thriving.)
Additionally, although RC is abandoned, but not "forgotten". Said convoys might clear away stuff that gets in their way. The trio got out at the end of Re2R looks more like a prairie. And it does look like in the map that it's a flatter area, even if you need to drive through a mountain to get there. So maybe the trees we see in the city were mostly planted by humans and the actual vegetation should be prairie-like, peppered with pines where the habitats mix? It's a stretch, but RC could have its own microclimate (huge still running complex underground, all that concrete and the buildings) that doesn't support endemic flora.
No animals (other than that one boss)? Again, chemical pollutants, zombies, and other mutants. Probably.
