I don't want to dismiss your personal experiences, but I think that's the wrong conclusion to draw.
Common mental illnesses - particularly depression and anxiety - have incredibly high placebo response rates. Everything looks like a promising treatment for depression in an uncontrolled trial. You can pick practically any intervention - including literal sugar pills - and get ~40% remission rates in an open-label pilot study. Many thousands of potential treatments supported by plausible theories, anecdotal accounts, case reports and small uncontrolled trials have fallen flat as soon as they were tested rigorously. The base rate suggests that the chance of a keto diet (or any other intervention with this level of evidence) being an effective treatment for depression is on the order of 0.1%.
If keto works for you then you should stick with it. The problem is that it's overwhelmingly likely to be no more effective for other people than a low-fat diet or a low-GI diet or sugar pills or faith healing. Articles like this one do a huge disservice to patients, because they completely neglect the base rate and perpetuate a cycle of hype and disappointment that can ultimately lead to distrust and despair.