What finally cured me of any notion of progress in philosophy as a thought-tradition was reading a history of philosophy from a philosopher that I respect; and who has argued well in favour of the potential for philosophy to be the kind of subject that does exhibit progress.
The book is: Alasdair MacIntyre. God, Philosophy, Universities: A Selective History of the Catholic Philosophical Tradition. Lanham, MD: Rowman & Littlefield, 2009.
To me, in contrast, the book showed nothing but the zig-zags of academic fashion.
On the other hand, my own personal and self-validated philosophy has indeed progressed - from incoherent harmfulness to something much better.
So, solid experience confirms that philosophy is objective and progress is possible for an individuals during his lifespan. But not at the group level and across generations.
This explains why real philosophy has often returned to the primary sources (e.g. reading texts by Plato and Aristotle - or at least translations) - because the subject of philosophy is one that is encompassed by the life of a Man, and is learned and developed during the life of one Man.
And therefore the subject of philosophy is an encounter between individual Men (often across the generations).
This explains why there is no agreed objective definition of philosophy - there is not even an agreed canon of valuable philosophers; because there is no valid extra-personal arbitrator - you or I must decide 'what is philosophy' for our-selves, and for our own actual purposes in the context of our own lives. And this definition may, probably will, change through a life - according to actual needs that 'philosophy' may address.
For instance, I have had some use for Plato and Aquinas; but none at all for Hume or Kant - because I have been sure (from secondary sources) that Hume and Kant's work is fundamentally metaphysically wrong, that they work from false - therefore evil - assumptions.
To the extent that studying them thoroughly is harmful - and that harm can be confirmed in those who have studied them and promote them - and why would I want to harm myself?
For me, philosophy has been therapeutic in the way that Wittgenstein claimed it should be - but failed to achieve in his own work. The therapy has come from showing that some of my assumptions were indeed assumptions, and were not 'evidence', were not conclusions. I only arrived at this situation in late 2012, I think - so for most of the time I read and thought-about philosophy (about 40 years) I was wrong, it was wrong, and it did more harm than good.
But in the end, a few specific bits of philosophy (including from people not recognised by academia as 'philosophers') has been greatly valuable - life-saving - living as I do in a culture for which the mainstream philosophy is so massively harmful, so powerfully inculcated, and so deeply embedded.
This post originated in a comment at Bonald's Throne and Altar blog.