This isn't true at all. There are (undocumented) artificial costs to all instructions, making something like writing a performant software 3D engine non-trivial. For example there is a benchmark cart that compares runtime performance of multiple triangle rasterizers (https://www.lexaloffle.com/bbs/?tid=31478). If the limit was the host computers ability to execute Lua you'd be able to trivially draw 10s of thousands of triangles in software without issue.