Especially taking care when writing the outer voices is sound advice, I'd say (and something I've seen a great many music theorists recommend). The outer voices are normally more audible than the inner voices, so it's particularly important to compose them gracefully, whereas the inner voices can get away with being relatively bland. There's good precedent for this approach, as well, given that Mozart, one of the most brilliant composers, is said to have started by writing the outer voices and only later filling in the middle ones.