You say this but do they actually plug holes? DT has been an issue for a few years now. S has been an issue for a few years. They draft a lot of CBs and basically have only one they can count on left on the roster. And at the end of the day, you can't fill every hole with a competent player you just got in the draft. You have to use FA wisely.
The Cowboys suck at FA and it hurts them year after year. The results speak for themselves. You see a warm body signed in FA and think, good job, they filled a hole. But if the guy can't play and make an impact, is it a good job?