The substance a good dsl for implementing rewrite/string substitution systems, as well as (likely high-quality) implementations of algorithms causal invariants, knuth-bendix completion, graph isomorphism, etc. [1]. A lot of that pre-existed the Wolfram Physics Project. The new thing appears to be:

1. a rebranding with improved documentation / learning resources for using those features (hey, documentation is hard! discoverability matters!), and

2. a set of really impressive rendering algorithms for visualizing these sorts of systems. (hey, visualizing mathematical objects is quite substantive! I'll happily pay good money for "low-effort pretty charts"!)

I addressed in the companion thread why I don't think this is particularly likely to result in "a new type of physics": https://news.ycombinator.com/item?id=22866284

Mathematica is good software. Pre-wolframengine I did shell out the $2K for Mathematica because it contains best-in-class implementations of some important algorithms. A high-quality reimplementation that matches Mathematica's performance would take me several years (in an area where I have a phd). Wolfram Research employs smart folks and lets them spend their time writing really high quality code, and the only way to access that code is by calling Mathematica's built-in functions.

But just because the goal is perhaps a bit grandois and the presentation definitely breathless doesn't mean there's "nothing of substance".

[1] https://www.wolframcloud.com/obj/wolframphysics/Tools/guide-...