"I'm doing good" instead of "I'm doing well" "He eats real fast" instead of "He eats really quickly"
If enough people speak that way, I don't think you can call it "wrong" so much as a dialect in its own right.
Fast and good are de facto adverbs. Maybe in some American dialects it's common to use other adjectives as adverbs, but not in mine.
Agree that language changes.
You just triggered an image of my first english teacher. 'To be plus adjective, adjective plus noun, verb plus adverb' was her favorite. ;)
"I'm doing good" instead of "I'm doing well" "He eats real fast" instead of "He eats really quickly"
If enough people speak that way, I don't think you can call it "wrong" so much as a dialect in its own right.