I have tried ZRemesher, and its prone to producing artifacts with meshes from CAD, which I don't think is the fault of the algorithm. CAD meshers in general don't care about producing sliver like triangles. The meshes are typically intended for 3D printing and generally these sliver triangles don't present an issue there. It's possible the polygroup retopo method would still have issues with these triangles.

Its possible the issue is with normals, although I would need to look at it further. The difference between facet normals and vertex normals could be relevant. Perhaps the issue is not so much with the proportion of the triangle, but how the normal is calculated for that triangle. In the end I don't really care whether its a geometry issue or a normal issue. I just want a nice render that doesn't cost me a lot of time to remesh/retopo.