I'm sympathetic to your point of view -- I remember the "independent investigators on reddit" wrongly accusing Sunil Tripathi of being the perpetrator of the Boston Bombing and causing his family a great deal of distress. But the author provides a few salient examples of why relying on "professional investigators" has come up short:
> The official report also did its best to paper over a number of failings that contributed to the plane not being found. In addition to the long delay in informing authorities — caused by missteps at the Kuala Lumpur and Ho Chi Minh City control centers, as well as at Malaysia Airlines — criticism should have been levied at the Malaysian military. Why didn’t they intercept the unidentified aircraft as it was crossing the north of the country? The military claimed it was because the plane wasn’t a threat. But how could they have known that unless they had identified it as MH370, rather than a foreign incursion? And if they had identified it as MH370, why didn’t they tell anyone until days after the crash? The most likely explanation was that the military simply wasn’t monitoring its own radar at the time that the plane flew through Malaysian airspace. But admitting this would expose a massive security vulnerability by revealing Malaysia’s military to be dangerously incompetent. Probably for national security reasons, the official report had nothing to say about this at all.
Seems like this is a pretty serious omission.
and
> Zaharie’s social life was also not as smooth as Malaysian authorities portrayed it to be. A combination of the leaked police report and interviews with people who knew him revealed that he had separated from his wife on an informal basis and was living alone in the family home.
So in essence Malaysian police were obfuscating the facts around the pilot, for whatever reason they may have. Perhaps they concluded based on further research that the pilot was probably guiltless. But whatever the reason, we do know that what they said in public diverges from what they found in private.
It seems to me that independent investigation and open source intelligence of this kind can be useful when there may be reasons for the official investigators to cover up certain parts of the story.
Lastly, I think there is a substantial difference between a crowd of people online with no real investigatory track record accusing someone (a la Sunil Tripathi) in the days/hours/minutes after the incident, and someone with a proven track record of credible investigatory reporting and some subject matter expertise, laying out some mixture of facts/theories/conclusions (that have already been circulating online) ten years after the fact.