Yep, I've worked for two companies where Fortran handles all of a major department's business - in both cases it was buried deep under layers of more modern stuff... but it was hugely risky to change it so it stayed.

While the argument is generally correct, Fortran and COBOL aren't in the same league. Fortran is still being upgraded and has some use cases that are hard to achieve in another language. I've seen the Rust subreddit recommending use of old Fortran code with Rust, rather than rewriting it in Rust. Unlike most other languages like C++ and Rust, Fortran kept its scope mostly limited to numerical processing - making it still one of the best solutions to code highly parallel numerical algorithms in.

Fortran isn't surviving just because nobody wants to rewrite Fortran code. Unless you're talking about Fortran77 code.