Regarding this 'good/bad mod list' that's sparked so much debate, I imagine that accurate physics are incredibly hard to get right for a whole host of reasons such as access to OEM data, interpreting that data and feeding it into a physics engine with its own inherent limitations, and then doing whatever else is necessary to fill gaps and correct anomalies so that the car also 'feels' subjectively right based on the modder's own expectations and - in rare cases - feedback from actual professional drivers or car owners. A lot of that is probably way beyond the knowledge or capability of your average Joe Modder, if they can even find the data to work with in the first place.
But a good point is made about the aesthetics of mods. Kunos literally provide a pipeline of instructions detailing how materials and shaders should be used to achieve realistic results within the AC graphics engine, but unfortunately this seems to be largely ignored by the majority of modders. It could be argued that, geometry aside (and most modders seem to have at least basic 3D skills now to improve or adapt wireframe models), there's no real reason why car mods (and in particular, cockpits) shouldn't
look almost as good as original Kunos content. There's no mystery to this, no secret shaders that Kunos use, no proprietary software - it's all spelled out by the developers themselves, and textures and shader values can literally be harvested directly from Kunos content. There's no reason why satin chrome on a door handle of any vintage car mod shouldn't look
at least as good as that from the in-game 250 GTO, because Kunos literally demonstrate exactly how to achieve that look and even provide the tools to do it. Some modders have always realised this and have achieved great results with their conversions for years (for example
@Showmebest66 at Assettodrive, and Markos Kass) but the majority don't seem to grasp it. Or maybe most modders just use the default textures created during the conversion rather than replace them with Kunos equivalents, then try to tweak shaders to improve them, effectively attempting to make a silk purse out of a sow's ear rather than starting from a good base. Seems crazy, doesn't it?
I don't know, maybe Kunos didn't do enough in the early days on their official modding forums to promote correct use of their workflow, or maybe they did and people think they know better. But it can easily be argued that the vast majority of car mods should look an awful lot closer to original Kunos content if only the instructions thoughtfully provided by the developers were actually followed. Thankfully, standards do seem to be improving overall but it seems to have taken an awful long time to get to this stage. Almost all of the recent ACC car conversions look to be on a par aesthetically with their Competizione counterparts, but the default shader values probably transfer better between these two titles than they do from doner cars from others sims.