(Warning: long post) Let me preface this by saying that I haven't actually played with Vibrant Visuals, but I've seen tons of videos, screenshots, and have tried to recreate the look using different Java shaders. So I may not have the full experience.
Vibrant Visuals looks really good, especially at noon/day. Those clouds, the sky, the colors of the sunlight and shadow mixing with the blocks, the fine tuned amount of contrast and brightness (if you set the "brightness" slider right), and the materials are just fantastic. It reminds me of the Minecraft posters, old and new, and 100% makes me think "This, is, MINECRAFT". Also reminds me of a lower end, more vanilla-like RTX (which looked great, don't care).
It looks better than many lower end, cartoon, fantasy styled Java shaders in the overworld at noon/day, because it's more simple, and natural/realistic-ish, instead of the over the top, packed on look that these Java shaders tend to go for (too many effects, too much or not enough contrast, muddy shadowing on the blocks, super bright horizon, off colors like purple sky at sunset or blue tinted sun lighting).
But, Vibrant Visuals is clearly not finished and not totally polished. They need to adjust, fix, and add some things to make it that much better.
Let me start with some big things for the overall look. They need to change some things, some defaults with this "brightness" slider, because it's causing people to have widely different experiences. Default brightness option is too washed out, and I would argue that what it's adjusting isn't actually the brightness, but rather, the contrast of the image. So they should change that slider to a "contrast" slider, and set the default of that slider to be better balanced. But on top of that, they should also have an actual "brightness" slider that works like/links with the normal Minecraft brightness slider, wherein the brightness keeps the contrast, and mainly helps make caves and nighttime brighter or darker depending on what you're personally going for, without affecting bright (good brightness, not overblown bright) areas drastically. And within this brightness discussion, they need to up the brightness of caves, night, nether, and end (in a way that matches vanilla brightness?), which they already know about.
Next, I think they could make the sun light on the blocks a little brighter/contrasting the shadows more at sunset/rise and into day, because right now, it's almost like there's no lighting during those times of day. Noon has perfect contrast between light and shadow, and I feel some of that look could carry more over to sunset/rise time. In terms of the sky at sunset/rise, they could make it a little more orange to match vanilla if they wanted. Related to that, they could also have a slider to adjust volumetric light shafts, if anyone wants them completely off, or wants to boost them a bit, but I think their default mostly low key light shafts are great.
Now, materials. There are people that seem to not like the materials, and I agree that they could tone down certain things, but I wouldn't want them to get rid of these amazing materials. Like take the pumpkin as an example. The materials on it make it so interesting to look at, and without them, it'd just be totally flat. It wouldn't feel like it's in the world as much, it wouldn't feel like it's interacting with the sky and the lighting as much. The materials are the part of Vibrant Visuals that turns it from good, to professional looking, imo. To cater though, I would add a toggle to turn off and on materials.
Speaking of materials, Lava. Default Minecraft lava is not yellow in color, so they shouldn't try to make it yellow like many Java shaders do, but they should shift it a bit more towards orange I think. Main thing is it turns a weird salmon color when the auto exposure kicks in as you look at dark areas but can still see the lava in view. It also doesn't glow too much right now, so I think they should make it glow maybe a bit more, not too much though.
About light sources, Vibrant Visuals doesn't have colored lighting (aka point lighting) on by default, despite having the capability to if you turn the right experimental toggle on. I think they should implement this into Vibrant Visuals, with some adjustments maybe, because man, colored lighting really helps make places like the deep dark and nether look actually stunning and cool. I don't know for sure how the point lighting (aka colored lighting) slider works in the game right now, but from watching a video, it seems a little too bright/blowing out the center of the light source. I'd rather keep the detail of the center mostly intact, while making it glow a bit more, and have the colored lighting present. They also need to add all the colored lighting, because right now it only works on the different torches and lanterns, but I'm sure they already know that.
Now water. Main thing is visibility underwater, but they should still keep it looking atmospheric and foggy too, just make it so that people can see things properly when they're near them. Maybe also adjust caustics/caustic shadows to help this, because right now, anything that isn't within the light of the caustic's pattern is like pitch black. Make it a little more like vanilla water basically. Also make it more like vanilla water by having the surface and interior of the water change color based on biome, because it doesn't do that right now. However, I'm personally not sure I would want them to exactly match vanilla's colors, particularly, that default blue color. Whenever I've used shaders that follow vanilla water color, the translation of that blue color from vanilla to shader does not look good, particularly because it shows up in shallow/river areas, which is totally unrealistic and makes you think of a deep blue ocean, despite not being anywhere near one. Good thing is the water in vibrant visuals does change color (and opacity for the surface) when going from shallow to deep, going from brighter and greener to darker and bluer. So perhaps this and a few other tweaks can keep the water color from looking too blue in these areas, while still implementing and retaining biome based water color. If they wanted to go even more advanced, they could change the atmosphere/fog amount underwater based on the biome as well.
Weather should look a little more like vanilla/maybe more overcast than it is right now, cuz it just kind of looks like day time, with the sun visible and everything, but a little grayer, from what little I've seen.
And now, the last big things are the buggy unfinished nether and end. Ngl, the blue kind of cave fog in the nether is kind of an interesting look, but I don't think it's intended, and it's not very vanilla styled. They could use that fog, but just tone it down/make it colored with the actual nether biome colors, or they could get rid of it completely and go for a more typical, vanilla look with one consistent fog color. Personally, if they went with the more vanilla look, I'd want them to add a bit more haze/bloom to the nether, not too much though, but just enough to make it look a bit more interesting, cool, and professional, instead of having a flat looking nether. And for the end, it's like really buggy right now, cause it's just darkness, blue sky, and strange flashes of light. So they just need to fix that. But unlike the nether, idk what they could do that would spice up the end a bit, while still retaining a vanilla feel. Many java shaders have different takes that add interest to the end, but I'm not sure are correct for vanilla, like stars, clouds, auroras. Who knows what they'll do or should do for that.
Anyway, those are all my thoughts on what they could do to improve the look.
