Off to a good start for your crash course beginning with Artlantis. Ignoring composition and the story being told, you've no doubt noticed a few things right away about your image, I'm sure:
1. Bad tiling pattern/repeat for the gravel (?) in the foreground
2. Light color / uninteresting pattern for the grass in the background
3. Strange dark line at the horizon
4. Washed out, and uninteresting texture on the wood framing in the foreground
The over-exposure of the sunlit surfaces is due to your settings for the power of the sun and sky. It looks like you set your sky illumination high to avoid dark shadows (and good to see blue-ish shadows). If you want hard edges as shown, then bring down the sun power/etc. Or, change your sun shadow casting to a softer setting and adjust sun/sky power as needed.
There is a setting that lets the auto-generated clouds affect sun power/shadows. That can result in an improvement some times. Try it.
For (1) and (2), I saw that you posted a question on the Artlantis forums and the folks there gave you the correct solution - just looks like you did not implement it? You need to adjust the material response to light, but most important is a combination of multiple quality textures with differing opacity settings so that each is visible as a blend, but with one rotated differently from the other so that the tiling/repeat is in different directions. Also, as suggested on the Artlantis forums, you may need to adjust your bump settings (which will slow down the render though).
For (3), the dark line at the horizon is no doubt because you did not insert the infinite ground plane in the scene inspector. Press cmd-I (ctrl-I) and add the ground plane, clicking on your lawn to set the height and then applying your grass teture to it.
Even with that, it will look odd going off infinitely to the distance, a quick fix is to insert fog way in the distance and low to the ground, and using either a grass green or sky blue color. This creates a band of diffuse color which makes the sky and the ground blend together like a gradient fill. It will still not look natural, but it is a quick fix for prelims. If the real image needs this viewpoint, then you need to place curved wall in the distance upon which you place an alpha mapped (transparent to sky) image that creates the illusion of what is really in the distance. Dwight Atkinson gives many examples of this on these forums (cyclorama) and in his books.
For (4) you need either a different texture if you want the woodgrain to show, or you just need to add some noise so that the surface does not look so clean. (Ditto the very cool leaf structures above.)
HTH,
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sonoma 14.7.1, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB