I agree with some of the author's points - for instance, that mere morality is not transcendent; that what we really need is to love God with all our hearts. A person can be very moral, all for self centered reasons that have nothing to do with wanting to serve God in love.
But at the same time, if the culture is hellish, as it is now, peoples' hearts become harder and harder the more egregious and vicious sins are accepted as normal and natural, thereby making it more difficult for them to hear God in their hearts or respond to His voice.
I also disagree that there is no Holy Spirit in peoples' hearts; my study and practice shows me that God is indeed in everyones' hearts, the Soul of our soul, but most of us don't hear Him much.
But that's a fine point.
The problem is this belief is unScriptural and leads to a real misunderstanding of God's creation. But it is definitely the mantra of modern man.
The idea that God is actually "in all of us" is a gnostic, Platonic concept which permits man to think of himself in God-like terms and abilities apart from Christ. All sorts of mischief and error results from not understanding the difference between carnal man and spiritual man.
Only God saves. The ears with which we hear or ignore the Gospel were created and given by God, according to His plan for salvation from before the foundation of the world.
"What then? Israel hath not obtained that which he seeketh for; but the election hath obtained it, and the rest were blinded
(According as it is written, God hath given them the spirit of slumber, eyes that they should not see, and ears that they should not hear;) unto this day" -- Romans 11:7-8.
Jesus answered them, I told you, and ye believed not: the works that I do in my Father's name, they bear witness of me.But ye believe not, because ye are not of my sheep, as I said unto you.
My sheep hear my voice, and I know them, and they follow me:
And I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand.
My Father, which gave them me, is greater than all; and no man is able to pluck them out of my Father's hand." -- John 10:25-29.