Maintaining state and mutating state is useful and neatly done in OO. That is, when done right, which is hard. I certainly agree that for processing data, good functional languages reign supreme. They are usually terser while more expressive.

It seems that solving problems need their own tool. Compilers typically fit a data processing pipeline. Yet, a use case such as editing an AST (e.g. a text editor showing incomplete syntax state) probably could better use OO as a tool.

Most current software then simply uses the wrong tool for the job; they do data processing with OO, and state representation and mutation using functional pure idioms. A problem that is not yet solved very well in the industry is interplay with these idioms. .NET with C# and F# comes to mind, which allows for easy workflows leveraging both OO and functional.