Apple can't do anything about the underlying technological reality that there's a big difference between current consumer desktop platforms and current workstation/server platforms. They're also being hurt by the fact that the base configuration Mac Pro is quite different from the typical configuration Mac Pro. For consumer PCs, it's common for the base model to be one of the most popular configurations, but for the Mac Pro the base model is a niche product that relatively few customers will opt for. This defies the expectations of people who approach the Mac Pro as if it is a consumer product.
That's not true. Threadripper has more cores, supports more memory, has 6-channel memory, more PCIe-lanes and so on.
Even the AM4 socket will soon have 16-core CPUs and PCIe4, so it will probably have more bandwidth than any Mac Pro, for a few hundred USD. The world is moving fast, that's for sure.
And yes, AMD's consumer desktop platform is getting a substantial update next month that will put it well ahead of Intel's current consumer desktop platform. But PCIe 4 is also driving up the cost of that platform quite a bit, at least in the near term.
Presumably the next gen Threadripper platform with PCIe 4 will launch not too far off the time the new Mac Pro does.
As has already been pointed out, the base model is pretty much irrelevant and that Threadripper system would probably be maxed out. Also that systems wouldn't run Mac software.
Everything you say is entirely true, but most people buying these new Mac pros simply won't care because it's not relevant to their actual requirements.