And yet here we are with a failed product. I think it's OK to ask why and consider its shortfallings. Obviously there was something, and I don't think it's fair to completely coast over the technology side of things and blame it on "marketing".
I think RethinkDB's marketing was excellent. The unchecked praise you mention is likely in no small part also a result of this.
However I don't think that means the technology was the problem. There are far more broken and misarchitected pieces of technology that are financially successful.
What exactly went wrong is speculative until we see the insights Slava promised, but it seems the failure was entirely financial: they had a great product, they brilliantly marketed it, but that didn't translate into sustainable revenue.
You seem a bit worked up, and it's hard not to read your comments in this thread in a tone which suggests you feel like you've been robbed of something.
These people don't owe us anything. When a company decides to open up and publish a postmortem it's a great and wonderful thing, but it's in no way obligatory. Even if their technology doesn't hold a candle to your expectations or the market's needs, it's still not without merit. If you want to learn, they've already given plenty for you to learn from. Rather than demanding more from them, be thankful for what they have already contributed.