Hello! This is my favorite resource pack, ever. Glad to see that it finally got updated and that you are working on it, my own attempts to do so for private use were not always up to the high standard of quality you set up with the 1.9 version. Unfortunately, to be very honest, I feel that some of your new additions don't live up to that standard, either. I do not mean to dishearten you, and I really hope that you'll continue your magnificent work on this resource pack.
The Crimson Nylium and Warped Nylium, while look good on their own, display a rather nasty tiling effect when viewed in a group, and the same is true, although for a smaller extent, for the Nether Wart Block and Warped Nether Wart Blocks. Making them in a way that all sides of the texture could tile with all other sides could allow them to make use of Optifine's Natural Textures feature, and solve this problem.
Having tentacles as the Crimson and Warped roots is an interesting idea. However, this texture is much less fuzzy than other grass-like plants, the details are much more clear, which means that it's much more obvious that each and every patch of roots looks exactly the same, they could use some variety! The colors also seem off, the Crimson Roots are OK-ish, but perhaps could use a bit less saturation to match better with the Crimson Nylium, and the Warped Root's emerald green color is very distinct and could use a LOT less saturation to fit in. Further issues with the roots is that they have white-ish pixels near the edges, a result of semi-transparent pixels in the PNG files, the Crimson Root, when placed in a pot, becomes a completely different plant, and the Warped roots just plainly don't fit inside.
The new Blackstone-derived blocks are just simple recolors of the old Stone Bricks, which is kinda lame IMHO, and the Waystone block seems to be a similarly low-effort creation. And now for the stuff that actually looks horrible: Souls Soil blocks, and Red Netherbrick blocks. These are literal eyesores, please, change them. The Chain's texture is also kinda bad. The white-ish pixel issue mentioned about the roots is also present for the chain, and a handful of other stuff. The Campfire is completely at odds with the rest of the texture pack, both the fire effect and the wood beneath it are completely different from the simple fire and wood textures in this resource pack. They don't fit well together.
Another thing I noticed is that the new Netherite items are just recolored Iron items. This doesn't make sense, as the basis of Netherite items are diamond items. There are noticeable differences between the shape of iron and diamond tools and armor, so this mishap is clearly visible, though I understand that it's a minor thing, still.
Some of the old stuff could also perhaps use some polishing. Namely, the Soul Sand texture. It tiles very badly, and it appears in large masses in the Nether, making it an eyesore. For this I'd have the same suggestion as I had for the Nylium blocks. The same is true to a lesser extent for the snow layer, when covering large surfaces, it has a very noticeable, grid-like pattern of darker spots. Furthermore, the sand texture gets randomly rotated, and I can't make it stop even if I explicitly try to make it stop with the natural.properties file, this causes the ripples in the sand to be misaligned. Perhaps you'd have more luck trying to fix it than I had?