Even most FAANG companies are over 20 years old: Apple is over 40. Google, Netflix and Amazon were founded in the 90s. Facebook is the youngest one, founded in 2004, which makes it 18 years old.
Within those companies, there is tons of legacy software and some of it still runs some of their most important systems, despite large sustained investments in modernization.
If FAANG is that way, imagine what it's like at large banks or defense contractors which don't have a strong emphasis on modernization in their internal software engineering cultures.
I know of at least one FAANG retiring the DBA role. While there are huge piles of legacy code, I wouldn't bet on legacy maintenance being a good ticket at a FAANG.
Within those companies, there is tons of legacy software and some of it still runs some of their most important systems, despite large sustained investments in modernization.
If FAANG is that way, imagine what it's like at large banks or defense contractors which don't have a strong emphasis on modernization in their internal software engineering cultures.