It isn't "Low N" though. 45 adults for a clinical study like this one is actually a very respectable size, particularly given their measures (and their respective reliability/studies backing them).

Seems like every study I read non-science people accuse it of having too few participants, without even considering the type of study (clinical Vs. statistical) and measures (subjective Vs. objective, reliability, literature, etc).

This is not a "Low N" study. If you believe it is then explain the statistics or methodology problems.

Yes, that too. Also it's important to realize that each study is a datapoint unto itself, and over time these data points paint a picture. But even if the study is not the whole picture, we can still get a hint as to what that picture is shaping to be.