> But merely been less confident (that they are) in their thoroughness and in their preclusion of contamination, is much easier to claim and be correct while doing so.

But it's a trivial observation, and one that isn't actionable or testable. For the team to have designed and performed the instruments, experiments, data collection, and analysis to say "We're confident in our results and we have ruled out contamination" is substantive and is backed by data and actual experiments. For someone else to say, "I'm not so sure, I think it could have been contaminated," and then provide no actual argument or data on what could have gone wrong, is probably not a novel observation or comment. In addition, it's an easy thing to say (as you correctly point out) without putting oneself on the hook to show how or why.

Here's what I mean: we can confidently say about every paper ever published that "I'm not so sure." Here are the possible outcomes: (a) the paper stands the test of time, the result holds, and nobody remembers anyone who said "I'm not so sure," or (b) someone finds a flaw in the paper, works with the authors and they publish a retraction or revised paper, and then whoever said "I'm not so sure," can easily (as you say) point out how "they called it," all without doing any actual work.

I'd suggest reading every paper critically, realizing (as most people do) that the results are tentative, and either letting it go at that, or dig in and do the hard work to figure out what may be flawed in the work presented. Then work with the authors or publish a paper of one's own pointing out the flaw and the new resulting analysis.