I don't entirely agree with the overall assertion of this article. The author has some valid points, but I think it misses the forest for the trees.
TLDR: I think Fortran tooling and HPC clusters are a self-reinforcing local maximum. They are heavily optimized for each other, but at the cost of innovation and extensibility.
For example, we'll never get a fully differentiable climate model in Fortran. The tooling does not exist, and there are not enough Fortran developers to make a serious dent in the tooling progress made outside of the HPC world. The MPI stacks these codes rely on are not great for hardware outside of a supercomputer, and Fortran codes basically are built around full interconnect. I have many PFLOPs at my disposal that I cannot use because these codes are too brittle without being entirely rewritten.
At the end of the day, everything is a Turing machine, so you can technically do whatever you want in Fortran or any other language (or mix and match), but strategically staying in Fortran leaves a lot of resources on the table.