Old games like this have a small (and shrinking) audience of people who care about them. With Tribes 2, for example, there are only ~50 people who actively play on a regular basis. A subset of those people are programmers, and a subset of those have the time & energy to put into a project like t2-mapper, assuming they're even interested. I got a basic version working, but then Claude Code helped decode and convert obsolete Dynamix/Torque3D file formats (improving existing Blender addons that were incomplete), got TorqueScript running in the browser, wrote shaders, and generally helped figure out what the original C++ code was doing.
In the past, you'd need the stars to perfectly align for stuff like this to happen: a passionate super-fan with the time, resources, knowledge, and persistence to see it through. Now, you mostly just need the persistence (and maybe a couple hundred bucks for tokens). I foresee people with niche interests (but not necessarily a programmer's skillset) being able to extend the lifetime (and maybe audience) of their obscure or obsolete software.
Some of the custom features you may be referring to I implemented as custom properties in the glTF output - like surface flags. "Outside Visible" is one example, it's a flag baked into each .dif surface that determines whether rays can reach it from the outside, so the engine knows whether to apply the map's directional sunlight, or just ambient and light map lighting. So, even though it technically could try to render with modern PBR, dynamic lighting/shadows and all that, it instead renders as close to the original as possible using the same (or similar) techniques. Comparing screenshots with actual Tribes 2 renders is often indistinguishable unless you really know what to look for!