From your link: “There is a clear need for more rigorous, well-controlled, prospective studies to support a sophisticated, nuanced understanding of the plant,” said Swogger."
Nowhere in that story do I see anyone arguing that kratom should be legal for sale everywhere by any supplement dealer without a guarantee of content or purity, and that sellers should be able to make any claims they want.
If you lined up all the drugs that were felt at some point to have potential but never panned out or had serious limitations that precluded their use, you’d have a hell of a long line of drugs.