This....needs to be replaced ASAP

[Amnmaat]

After being OOB in several regions, the "ground" is just a flat grassy texture that's more akin to blobs, trees are 2D and are the sky box underside.

It's meant to fill in the blank spots not look like real life where there's something anywhere, and Yoshi P has gone on record talking about how a problem with 1.0 is that they were focusing on making every detail perfect when really- it has to be "good enough" and then move on. That random spec of land fits the good enough criteria and if you're going through the MSQ or anything on field- you will not notice. You really shouldn't notice. Only people looking for internet fights will notice.

Internet fight? What are you on about?

As for "good enough," that's subjective when the same background exists in other places with better quality.

To me, the only thing worth fixing is the damn awful AA used in this game. The shimmering is so distracting.

Yes, FXAA is the worst when it comes to AA solutions. You don't want to glamour glasses/shades on your character or you'll be looking at ants crawling around your face.