A simple explanation in proving the progress exist in subjectivity.
Although the war field of philosophy is more subjective than it is objective, it does not negate it’s potentiality of progressing. And by that, I do not mean the use of objective methods in overcoming seemingly subjective questions, but instead asserting that even in fields that are purely subjective progress is possible.
The crux of the problem lies from the nature of subject. But alone, it is not enough to assert that on subjective arguments, progress is intangible and unverifiable. One must not be confused between the progress is objective fields and subjective field. In objective fields, progress would simply mean a further understanding of our universe through empirical methods. Therefore, even to the non thinker, it’s prominent. But on subjective fields, since no absolute truths exist(by today’s standard at least), progress may only exist in the quality of thought and depth of answers/questions generated.
Philosophy can be practiced with mere thought. Whereas science must be practiced with thought, observation and experiments through falsification. Science deals with a body of methods in discovering constants and knowledge on our world. But in the field of philosophy, answers is not what that counts. Instead, questions and possible prospect to these questions, then more questions on these prospect.
To conclude, progress in science is determined by objective answers capable of simplifying equations on natural phenomena. But progress in philosophy is measured by elasticity of the questions posed. Therefore, in many instances progress is measured by the complexity of thought we are capable of modeling and finally the prospect to these thoughts. And even to measure the depth of thought alone, it’s enigmatic. But however complex and sometimes ineffable philosophy is, it does not shut it’s room for visible progress.