It's worth noting that Siegel's article seems to extrapolate from one paper (Shankman et al., 2017) 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). Usually in these kind of situations there's a lot of back-and-forth as new objects are found in the outer solar system and the analyses of systematic errors and biases in the various surveys are refined. If there is an actual detection of Planet 9, that would resolve things fairly definitively, the reverse situation is going to be rather more difficult to prove.
In response to the OSSOS paper (Shankman et al., 2017) 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:
That is,
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.
Batygin et al. subsequently posted a 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 9 as an explanation for the solar obliquity.
On the anti-Planet 9 side of things, it's worth looking into Kavelaars et al. 2019, a subsequent paper from the same authors as the study based on the OSSOS data, who note that there seems to be an absence of objects with perihelia ($q$) between 50 and 75 AU that would be expected if a planet was causing the alignment, which so far doesn't seem to be explainable by detection bias.
A survey
that might have detected a TNO at $a ∼ 500\ \mathrm{au}$
and $q ∼ 75\ \mathrm{au}$ is actually more likely to have detected objects with similar $a$ but smaller values
of $q$. The same is true of the other $q > 75\mathrm{au}$
detections: the lower-$q$ but similar $a$ detections
are always more likely. Thus, the lack of detections in the $50 < q < 75\ \mathrm{au}$ range may be indicating that there really is an absence of TNOs
on orbits in this range. This strongly contradicts models of orbital evolution that include
an additional planet, as the gravitational action of such an object would cause TNOs to
be distributed across a range of $q$ values at any
given moment (Figure 2; Shankman et al. 2017a;
Lawler et al. 2017). Thus, if the lack of objects
in the $50\ \mathrm{au} < q < 70\ \mathrm{au}$ range is real, the
hypothesized external planet can be excluded.
It still is an active area of research, so it remains to be seen how the various studies will hold up.
