I think abandoned is too strong of a word. Many research projects have an explicit goal of building an MVP (and an explicit non-goal of doing anything beyond that). The research project is only really "dead" when there are no more questions to be asked. Even well-known professors some times have gaps of years or decades when no apparent progress is being made, but may still pick up the problem later and work on it (see e.g. the STOKE project and Alex Aiken's previous superoptimization projects).
I don't mean abandoned in a particularly negative sense, exactly because it's normal for research project to be left behind as you describe.
But from the point of view of a potential user, this kind of software is undeveloped, unsupported and rotting away (e.g. about two Clang versions behind): probably useful as a prototype to plunder and reimplement, not as a tool to get things done.
