Her songs take on a completely different note when she sings them live. But yes the material generally doesn't always match up to the voice.
That being said it's an over generalisation. The first album has some great early 90s R&B on there, while the award winning second album is one of the most important albums of UK Soul. It's a fantastic album, and is not in any way bland.
Once the marketing machine took over from album 3, it all began to gradually go further and further MOR, but even on Who I Am and Affirmation there are some great pop songs.
I lost interest mostly after that, although in hindsight the Music City Soul album, while totally choosing the wrong songs as singles, has some absolute corkers in it as well, namely these which are anything but bland:
Even in later years, she still lets rip every now and again: