A user told me my product was useless and they were right

Got an email from a user last week that just said

"it's useless, I can't upload my 9x16 video."
No greeting, no context, just that.

First reaction was honestly a bit deflating because we'd put a lot of work into the product. but after sitting with it for a minute i realised they were right. We genuinely didn't support 9:16 uploads and that's a pretty big gap for anyone working with social content. So we built it.

9:16 support is live now and it came directly from that one angry email. Sometimes the harshest feedback is the most useful because there's no fluff to decode, the problem is right there in one sentence. No guessing what they want, it validates the need instantly.

Curious if anyone else has had a similar experience where brutal feedback ended up being the best thing for the product?