Do you have any links to, or can you share any more information about "modern" haskell? What's different?
But basically it's a meta-extension that flips on a bunch of extensions that most haskell users would come to expect as 'default'.
As a simple example: TupleSections. If the compiler complained to me that I needed to turn on TupleSections, I wouldn't take a minute to consider whether it was a good idea, I'd just be annoyed that I hadn't flipped it on somewhere already.
Actually that flag existing is part of why I think new books are being written, to start defining what "modern" (with all these flags on by default) haskell looks like.