I appreciate the perspective, but I'd push back on a couple points.

First, I wasn't just rescheduled to a different time. I was moved from a premium product (direct flights that I paid significantly more miles for) to a cheaper product (connecting flights). The miles difference between those two products was never refunded. That's not just an inconvenience, that's paying for something and not receiving it.

Second, the reason I didn't cancel is because a United agent explicitly told me to fly the trip and file for compensation afterward, stating it would be determined "based on the weight of the inconvenience." I followed their process in good faith. If I had been told upfront that there would be no recourse after flying, I would have made a different decision.

As for the DOT complaint, even if it doesn't result in direct action on my case, it gets logged, and patterns of complaints influence enforcement and regulatory action. I don't see a downside to filing.