Hi Gabriel,
I just wanted to add two little points that I run into as a Flame/Nuke Compositor when I receive 3D renderings, especially when the 3D artist is not used to work with ACES. I hope I explain it okay.
First the temptation of using Output-Srgb because the texture looks “right” at first.
I try to explain it this way: Think of the texture as a poster on a wall (srgb-texture) - ACEScg has a bigger gamut than sRGB that’s why the poster doesn’t look so colorful. Your poster can’t have all the colors that you can see in nature. The diffuse values of the poster are between 0-1, but 1.0 is not white on your display anymore it is just a scene referred light value viewed trough the RRT&ODT. In your case sRGB. If you find it too dark, just gain it up (multiply) or you can add to lift all the values of the texture. This is how colors on a poster will also appear when you film them with a DSLR for example. The maximum white on the poster is always white on your photo (in this case your viewer), but how bright the white will be depends on the exposure of the scene.
So using Output-sRGB will set a white on the texture or poster to over 16. This is a specular highlight value on a normal exposed image with the color chart that you are using. The only way I can archive this in the real world if my poster is at a bus-stop for example and has a light source behind it. Now the poster or texture is a light source by itself. This doesn’t make any sense to do this with your grass and soil texture on the rock.
The second point is the dynamic range of the HDRI that you are using, especially when you work in ACES or another view transform like FIMIC from Blender. In the past we viewed the 3D render and the composting through a SGB gamma tone mapping curve.
1.0 was full white so you had to be careful not to overexpose you rendering or comp (soft clip was helping you there). Working with ACES needs higher values to really light up your scene and no clipping or clamping of values. A simple HDRI will maybe clip/clamp in the lights or the sun at 3.0 or 300.0 depending how it is captured. But I need to have values of around 100.000 or more to mimic a sun with a clear sky on an outside captured HDRI around noon. Otherwise my lights are far too weak. I was testing this out with a Theta-S from Ricoh vs. a DSLR with a pano head and most important - a ND filter.
You can find a lot of examples here: https://www.toodee.de/?page_id=1309
Please try to use a HDRI with proper light values. The one in your rendering looks artificial? If you want I can upload you the one I was using here (https://www.toodee.de/?page_id=2258)
Best regards
Daniel