I work for a very large company that has a mostly SSR monolith written in PHP.
Modern PHP is a joy, and it's much faster these days, but performance is still a problem. It was chosen over 25 years ago, and I'm sure they thought the same thing about never getting the amount of load they eventually got.
Modern PHP is virtually indistinguishable from dotnet, with some php-isms sprinkled on top. They should've chosen dotnet all those years ago.