On objectivity versus the emotional and imaginative sources of Mahler's art, I recommend looking at the facsimiles of the 2nd and 10th symphonies. Mahler's revisions, impulses, reflections, and leaps of inspiration and sometimes despair can be seen in the Kaplan reproduction of his M2 manuscript. And, famously, Mahler's outpouring of grief and hope in either of the M10 facsimiles reveal what I take to be "profundity and human need."
I find Klemperer, while less of a subjective conductor than, say, Bernstein, to have a compelling understanding of why the M2 is important to us.
Best to all,
Tom in Vermont