> The sentence in question is:
"Wearing masks in the community probably makes little or no difference to the outcome of influenza-like illness (ILI)/COVID-19 like illness compared to not wearing masks (risk ratio (RR) 0.95, 95% confidence interval (CI) 0.84 to 1.09; 9 trials, 276,917 participants;"

That sentence is not in question. It doesn't exist anywhere in the review.
Please read the review yourself. https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD...
Here is the link to the full PDF: https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD...

In a statement about the review, Lisa Bero (the Cochrane Public Health and Health Systems Senior Editor) says explicitly:
“The results of this review should be interpreted cautiously, and the uncertain findings should not be taken as evidence that these measures are not effective."

You can find that here: https://www.cochrane.org/news/featured-review-physical-inter...

> I think we all agree with you (and thus, with Soares-Weiser) about the frustration (heck, downright confounding) resulting from the lack of evidence.

There is not lack of evidence on the effectiveness of masks to prevent/spread illness. There is a lack of evidence on the effectiveness of policy. This is not evidence that those polices are themselves ineffective. Quoting again:

"An updated review of physical interventions by Jefferson and colleagues assesses three commonly recommended interventions: masks, hand hygiene, and physical distancing.[2] They found evidence that masks had limited or no benefit in terms of preventing influenza‐like illnesses or laboratory‐confirmed influenza. However, except for a handful of studies, most of the evidence is from studies examining effects in wearers. An important effect may still lie in how masks reduce transmission of virus to others, which is more difficult to ascertain.[3] Resulting uncertainty in the evidence for public health measures has fed controversies regarding the legitimacy of public health policies involving these measures, with face masks being a special target for criticism.[4, 5]"

"For each measure, though, lack of evidence of effectiveness is not evidence that the interventions are ineffective. Rather, the details of these reviews show why there may never be strong evidence regarding the effectiveness of individual behavioural measures when deployed, often in combination, in a general population living in the complex, diverse circumstances of individuals' everyday lives. Waiting for strong evidence is a recipe for paralysis." (source: https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.ED...)

> Is it possible that a larger, properly-powered RCT will find that some form of N95 application will have some effect on community transmission?

Anything is possible, but it appears that any attempt at such a study would likely result in a failure to uncover actionable data. Reasons for that are explicitly listed in the source above which goes on to state the following: "However, while there is reason to believe in the combined effects of multiple behavioural measures, there is not, and may never be, high‐quality evidence from randomized trials on those effects."

RCTs are a very useful tool, but they aren't the right tool for every circumstance. This appears to be one of those cases. It's fortunate then that we don't need to depend on them in every circumstance. We can have an extensive pool of other types of high quality evidence to draw conclusions from. We have lab tests where we have no issues testing the physics involved in different kind of masks blocking virus-sized particles on simulated inhales and exhales. There have been RCTs involving health care personnel which show that worn correctly and consistently masks work. The effectiveness of masks to help keep people from getting and spreading disease is not really in question. The questions we do have, aren't ones RCTs are likely to help us answer.

If someone comes up with some way to perfectly control, and fully and accurately observe and record the behavior of large populations 100% of the time for the entire duration of the trial, and can do all of that ethically, then you might get the perfect research you'd love to see. Until then, we should focus on what we do know with confidence and what we've learned through other forms of high quality research.