The Gen 3 figures had enough polys to create detailed, life like sculpts without the need of any "super secret PA-only tools". Heck, I did my first sculpts by using hundreds of Poser magnets.

V4 had fewer polys, G1 even fewer, G2 a few more, and now we're back to fewer again.

So, how do I create DETAILED sculpts with such few polygons without the HD tool?

To an extent this is a discussion that was had when Genesis came out, before we had HD morphs. A partial answer is that in V3/M4 and V4/M4 you also didn't have SubD, so any smoothing had to be in the raw morph. With Genesis # the figure is SubD, so the smoothing that you had to sculpt can now be left to the application and you are able to make full use of the available resolution (which is, roughly, only one division down from the pre-Genesis meshes). For your own use, though I'm not aware of a way to share it, you can also adjust the edge weights with the Geometry Edit tool on a finished sculpt, though you can't link edge weights to a morph so that may not be of any practical use.