To give context, a lot of the modern materials are filled with baked-in colors that cannot be changed. The 4 materials at the top here all have random colors like black and brown mixed in that make it impossible for them to look like a low-contrast white (255, 255, 255). Similarly, the bottom row of materials have light colors baked into them, making it impossible for them to look like a solid (0, 0, 0) black.
Credit where credit is due however, the latest addition of 2024 materials (leather, plaster, rubber, cardboard, roof shingles, etc.) do not have these problems. The problematic materials were mostly a result from this 2021 set of materials where a lot of feedback was ignored.
I feel MaterialVariants are an easy cop-out to argue that the ‘old materials vibe’ can be replicated. And yes, from an engine perspective they do offer the necessary features. In fact, the image kostis shared is from my game(!) I worked on in 2016. And the modern materials aren’t good enough to replicate those feels, so I made my own pack of materials that do replicate the old feel.
However, this process took 2 months. Most developers do not have the skills or the time to create their own material packs that mimic that Roblox-y feel, hence why many developers are still sticking to the pre-2020 materials.
Regarding this bug report, if the issue described in the OP is indeed related to the linked bug report I made; I spoke to someone at RDC and they mentioned this bug was scheduled to be fixed in a few quarters. Given that RDC is coming up again soon, an update would be appreciated!