that these screenings are not all they’re cracked up to be

FOR decades women have been told that one of the most important things they can do to protect their health is to have regular mammograms. But over the past few years, it’s become increasingly clear that these screenings are not all they’re cracked up to be.
Could someone please explain the bold part?

idioms.thefreedictionary.com/be+ … d+up+to+be