There's a huge range between not "that special" and "lost"
A "Lost" decade that includes a grand-slam (1 of 3) in what's usually described as "Their greatest year in the modern era", another 5N title (making it 2 of their 14), 3 2nd places, a RWC SF (best ever) and 2 RWC QFs (both lost to NZ), 2 of the top 5 scores ever by Scotland (and both older than the other 3), including the era of their 2nd top try scorer in history is... stretching the definition of "lost" to mean "about the best ever by this country"
They may not have been the best in the world at any point, but it was far from "lost".
Scotland have been playing international rugby for 15 decades; I doubt you'd find more than 1 or 2 where they performed better than the 1990s (actually, there's a challenge - which are all these decades that show their 1990s to have been "lost"?)