Many indie developers want to create games with classic PS1/N64-style graphics but struggle with the technical debt of actual old engines.
Create a Unity/Godot extension or standalone engine that makes it easy to achieve authentic low-poly 3D with modern development comforts.
Indie game developers would pay for tools that help them efficiently create retro-styled games without wrestling with legacy tech.
MVP could be just a shader pack and asset pipeline for one major engine.
The risk is niche appeal – the market for intentionally retro 3D may be smaller than for pixel art nostalgia.