Grumbling about how typeclasses could just be normal datatypes has been an undercurrent in the Haskell world for a long time, particularly as a way to solve the orphan instances problem. However, the syntactic grease provided by typeclasses is pretty appealing, and in the end I think this may have died down because people developed engineering solutions to the orphan instances problem (mostly "don't") that mitigated the theoretical problems enough that even most Haskellers don't care anymore... but I guess a few do still somewhat, because such things never truly go away.

(And yes, I recognize the quoted sentence as being humorous and labeling the entire article as not entirely serious... my point is that it is not entirely unserious either. The idea has been kicking around seriously for a while.)