There seems to be no direct English proverb. However, "it's a long way to go in Xiu Yuan, but it's just Xi in Xiu Yuan" because Qu Yuan felt that his suggestion had not been adopted, and there was a long way to find the truth, which means it was hard to find the truth. You can consider the following proverbs and suggestions to see if they conform to your argument:
Truth is at the bottom of the well. Truth is hard to find.
Time is the father of truth. Time tests truth.
Truth and roses have thorns. Truth and roses have thorns.
In addition, you can also consider a sentence by Wilde:
Pure and simple truths are rarely pure and never simple.
English niurentuan