"Blanket characters"?
By that, do you mean well-rounded characters?
Not exactly. A "blanket move" is one that beats out a majority of options by "blanketing" over them. Such a move would be Sarah's 6P, for example. It beats out all highs, nearly every low, ties with the fastest mids, is decently safe on block and has follow-ups. Thus, you don't have to accurately read what your opponent is planning beyond are they gonna do a mid P hold, SS or random mid crush. Thus it's a blanket move.
The opposite would be, say, an expert high punch hold. You risk being HiC thrown, you eliminate the ability to hold a high kick and you'll be struck by any attack that is not a high punch (you also have to time the hold just right). Thus, it's a "precision read" move, in that it only beats out one specific option, but gives a good reward for doing so. Anything but that one read, though, and your opponent wins.
Characters who rely more on (or have more of) the former type are who I consider "blanket" characters, whereas those who rely on the latter are "precision read" characters. Personally, I feel like the latter are more difficult to use, for the reasons described above. They require more diligent yomi, I feel.