I brought this up on the AllCoreDevs channel and there was the usual criticism, but more support for the Yellow Paper than I expected. People liked that there were formal specs, but wanted there to be one that they can read as well.
The math in the Yellow Paper is not that advanced, (anyone with a year of so of undergraduate study can handle it) but it’s badly presented. And the English could be much better, as in the Beige Paper. But with effort people who need to read it can, and without learning another language first. And with effort it could be much more readable.
Compared to technical English and basic math very few people can read formal specification languages, and that terribly compromises many purposes of having a spec. For one important example, a spec that an engineer can use to write a client matters. For that purpose, for most engineers, the Yellow Paper falls short, but a K spec would be nearly useless.
To be truly useful I think our K spec would need to use a carefully designed presentation syntax, teach the reader the K they need to know, and be sure the embedding English is complete and correct without the K. Because in the end a K spec is a reference implementation in a language that hardly anybody knows. And reference implementations have well-known strengths and weaknesses as specs.
Still, it depends on who does the work, and how the community cares to put it to use. A number of people volunteered to get to work on a better Yellow Paper, including how best to embrace our K and Lem formalizations. Whether they do the work remains to be seen.