This is just my opinion
But yes, they are really that bad. We'll use the two different methods, 10:1 and Kuchera. The Kuchera method was developed to help provide a more "accurate: assessment of ratios after all, we all know ratios can vary significantly. But (and as far as I know...this is where I could be wrong, hence the "this is just my opinion) all these products do is take a ratio and multiply it by QPF.
Ultimately, snowfall production and accumulation are extremely complex and involve much more then just ratio and QPF. First off, snowfall ratios in themselves are extremely complex. They can change very rapidly during the evolution of the storm and can drastically within minutes.
Degree of lift, abundance of moisture/ice crystals within the snow growth zone, thermal profile, moisture, CAA/WAA, evolution of the dynamics are all extremely critical in snowfall ratio and accumulation.
Snow maps do provide value in they can help to quickly identify the gradient zones and where the cutoff can be expected and help identify local maxes and mins (the later though could easily be found by assessing numerous variable).