OP mentions "old languages" like COBOL and Fortran, which first appeared around 1959 and 1957, respectively. APL showed up around 1966, so it's in the same ball

OP mentions "old languages" like COBOL and Fortran, which first appeared around 1959 and 1957, respectively. APL showed up around 1966, so it's in the same ballpark era-wise. More to the point of OP's question, however, is the market share these languages command. I've read estimates that about half of banking software is still running on COBOL, somewhere in the ballpark of 100 billion SLOC or so. Fortran still sees active use in high performance libraries for scientific computing and supercomputer architectures, with solid C interop. Heck, a new Fortran spec even came out in 2023! In other words, COBOL and Fortran both still command significant market niches. APL, similarly, has on the order of several billion SLOC running around in financial and healthcare institutions, not to mention a long tail of data science applications. This is mostly true in the Nordic countries. APL the language is still alive and growing, getting yearly updates. Better yet, APL has a SotA compiler that can both host on and target GPUs. It's language model maps cleanly to hardware, which significantly eases reasoning about performance. At the same time it remains a high-level language where one can write production, performant, applications in just mere hundreds of SLOC, all while remaining pleasant to maintain and extend in my experience. Try saying that about any other language you know. That is to say, any accusations that these languages are "obsolete" are a bit naïve, IMHO. There are solid careers to be had as developers in each of their industries, without having to grind your soul to a pulp trying to find employment in IT just to end up writing yet another CRUDy SPA.