Radiosity was mostly used by laypeople (non-rendering specialists) to mean global illumination in general.
The actual specific radiosity algorithm (diffuse only, form factors and matrix solving etc) proved to be too unwieldy, requiring huge amounts of effort and care to get good results. This is in contrast to Monte Carlo path tracing, which doesn't require extreme care with meshing, doesn't assume diffuse BRDFs and is really well suited to modern massively parallel architectures. Consequently it completely took over production rendering, and game rendering is next.
The actual specific radiosity algorithm (diffuse only, form factors and matrix solving etc) proved to be too unwieldy, requiring huge amounts of effort and care to get good results. This is in contrast to Monte Carlo path tracing, which doesn't require extreme care with meshing, doesn't assume diffuse BRDFs and is really well suited to modern massively parallel architectures. Consequently it completely took over production rendering, and game rendering is next.