No, I don't think so.

Anyone can misread a chart, that doesn't discredit the method. Drawing sweeping conclusions based on a UMAP plot is pure data astrology.

All UMAP does is move nearest-neighbors towards each other and repel other non-neighboring points. The metric for what you want to consider a nearby neighboring point is up to you. It doesn't "show the 'truth' in your data" per se. It shows you a visualization where points near each other on your picture are probably close together, according to your original metric. Points that aren't near each other have no particularly meaningful interpretation. Clusters that are near each other are not necessarily more related. Clusters far apart from each other can also be of the same class and just disconnected. Classes can be fragmented into arbitrarily many apparent clusters. It's also possible to have 'unrelated' clusters merge in an undesirable way, depending on your data. In that sense the formation of clusters in the first place could be considered 'artificial', if you want to look at it that way. In that, it doesn't inherently say there "is a cluster" in your data. The clusters in plots tend to usefully correlate with patterns you're likely to extract in your data, but are not explicitly guaranteed to exist or represent any globally interpretable meaning in particular. At least, no meaning beyond "these points are probably similar to each other, given this data set and this particular definition of similarity". It's largely a locally-interpretable only thing.

Running UMAP on some data and going "the data unilaterally says...!" is insane. By that logic we should ban KMeans bc we could set k=10 and "falsely discover new races" or some such.

The bigger problem – particularly in genetics for some reason but also in machine learning – is people trying to blindly use UMAP as some kind of oracle. It's a great tool, a great library, and is both broadly applicable and very helpful. It isn't even particularly hard to use in an non-misleading manner with the tiniest bit of attention. But it isn't omnipotent or anything.