By "deep stuff" they obviously meant amazing ballads like "
Beautiful" and "
Hurt".
Christina keeps talking about these topics all the time and also sings about them.
I just remembered what M.I.A said about Lady Gaga... And honestly, I kinda agree.

Gaga keeps talking about being provocative not just
to be provocative, to make a change, to believe in yourself, to
be yourself, to love and not to hate, and etc... But, does she sing about it? Nope. All of her songs are about Sex / Partying / Fame.
I love Gaga though, but I'm still waiting for that inspirational song from her.