A lot of systems are obsolete, in the sense that you cannot find work in them. Nonetheless, people use them to prototype ideas that will eventually find their way into industry. Is Haskell obsolete? Not exactly, but it's hard to find real-world projects that use it. Concepts developed in Haskell get imported into other systems.

Systems are only truly obsolete when there is no real reason to use them. PL/1 is obsolete. It's hard to find even legacy code using it, and nobody would use it for experimentation.