This week Michael Brown and Konstantin Batygin released a new analysis of the clustering in the outer solar system, taking into account the OSSOS results that are the subject of Ethan Siegel's article. The paper can be downloaded from the arXiv. Brown also has a Twitter thread summarising the result. From the paper, their conclusion on the apparent absence of clustering in OSSOS:
the uncertainties in the measurement of clustering from
the OSSOS data are so large that OSSOS would not be
capable of confidently detecting the clustering seen in
the larger data set even if it were real and present in the
OSSOS data. Because of the limited survey region and
small number of detected objects, OSSOS observations
are equally consistent with being drawn from a uniform
distribution of longitudes of perihelion and with being
clustered in longitude of perihelion as strongly as seen
in the ensemble data. No conclusions on clustering of
longitude of perihelion observed in the complete dataset
can be drawn from the OSSOS data.
They do note that this does not necessarily prove the existence of Planet 9, but in the absence of Planet 9 there would still need to be an explanation for the clustering.
So it would seem that (assuming this new paper holds up to scrutiny) the OSSOS results may not be as fatal to the Planet 9 hypothesis as Ethan Siegel's article makes it sound. It's also worth noting that Siegel's article seems to extrapolate from one paper to "most scientists" without much justification, so it's not particularly clear what most scientists think anyway (and that's before we get into the question of whether the "most scientists" referred to includes scientists whose discipline is not astronomy-related).
Probably there is going to be a lot more back-and-forth over this as new objects are found in the outer solar system and the analyses of systematic errors and biases in the various surveys are refined. That is, unless there is an actual detection of Planet 9, which would resolve things fairly definitively.
Update (Feb 2019): Batygin et al. have posted a new review of the Planet Nine hypothesis on the arXiv, favouring a lower planetary mass and a less eccentric orbit than originally proposed. The new parameters do not favour Planet Nine as an explanation for the solar obliquity.