Is 'be thankful to your parents, for they brought you life' incongruent with Buddhist thought? It appears to me that this is incompatible with Buddhist teachings. Life will bring suffering, and it'll not be a kind and easy journey. So why be thankful?

On the other hand, if you weren't an arhat then you were going to be reborn in some way. If you were born in some type of affluent family with good values etc., then I guess you could be thankful.
From the Anguttara Nikaya 2.32

&quot;I tell you, monks, there are two people who are not easy to repay. Which two? Your mother &amp; father. Even if you were to carry your mother on one shoulder &amp; your father on the other shoulder for 100 years, and were to look after them by anointing, massaging, bathing, &amp; rubbing their limbs, and they were to defecate &amp; urinate right there [on your shoulders], you would not in that way pay or repay your parents. If you were to establish your mother &amp; father in absolute sovereignty over this great earth, abounding in the seven treasures, you would not in that way pay or repay your parents. Why is that? Mother &amp; father do much for their children. They care for them, they nourish them, they introduce them to this world.
&quot;But anyone who rouses his unbelieving mother &amp; father, settles &amp; establishes them in conviction; rouses his unvirtuous mother &amp; father, settles &amp; establishes them in virtue; rouses his stingy mother &amp; father, settles &amp; establishes them in generosity; rouses his foolish mother &amp; father, settles &amp; establishes them in discernment: To this extent one pays &amp; repays one's mother &amp; father.&quot;

Gratitude is a Buddhist concept. Below is an essay on Gratitude in Buddhism by Thanissaro Bhikkhu
Anguttara Nikaya The Further-factored Discourses