There is something noteworthy about GHCs language extensions. I was never bothered by adding one when it seemed somewhat useful. By no means to I understand the full implications of those (they also differ substantially in theoretical complexity).
The advances towards simple Haskell do make sense to me – thinking of bigger projects for bigger teams --, the concrete idea of going back to Haskell 2010 or Haskell 98 not so much.
Some sort of consensus on a set of language extensions that seems proven at least reduces potential confusion for a newcomer and helps creating some sort of standard.
What’s missing in the picture is a bold design choice: “This is what we think you should be able to do
with our compiler. This is feature is meant for use in production, this is research.”
“Duh”, you’ll say, “no-one can make an informed decision on that!” This is why GHC keeps it flexible in both directions (you can activate any extension, but none is activated by default).
It might be that any bold design decision is better than none, at the moment, even though no-one knows what the “optimal” direction of GHC really is. And really, the language extensions are just one aspect of that.