Unfortunately neither the original ThingLab nor the TypeScript reproduction are accessible to blind users -- in particular, the reproduction just uses a html canvas element.
I believe a fruitful area for future work would be to investigate using constraints to better support customizable accessible interfaces. For example, a UI toolkit could support constraints that fonts be at least 16 points, or that color schemes were accessible to a particular user's requirements. Something like the original ThingLab, but set up for good support for blind or low vision users, could also provide exciting options for exploring geometry, physics, and other subjects.