Posix lite didn't lose favor. It's still an important part of writing fuchsia native software. It enables us to use the c++ and rust standard libraries with minimal upstream changes. It was never meant to enable running all existing programs, only lowering the barrier. There isn't really much software that has been ported to run on fuchsia natively. Instead runners are implemented or ported and those provide the environment applications require. For instance a flutter runner, web runner (chromium), and starnix (a Linux runner of sorts) provide the basis of running many existing applications.