Why do ground textures in new zones look worse than in the old ones?

[MilkieTea]

Does the same apply to this comparison - https://ibb.co/WgrYSSm ? If yes, then why are they not using the methods that make the ground look less pixelated? It might be my eyes playing tricks on me, but (grassy) textures in new zones do appear to look much worse.

It does! brighter colors make it easier to see pixelations and artifacting.

Also,
They might be preparing to upscale textures soon and are leaving them like that to avoid extra work in the longrun. (By soon I mean in a few years when they phase out PS4 support)

Like if youre filling in base colors in an artwork before you go to bed, rather than leaving the colors empty.

This way, they dont have to remake textures, just upscale and touch-up later on.