I expect it not to be called sudoku at that point. Call it what it really is- a nonomino or kakuro or whatever.
And it's not called a sudoku, by the way. It's called a sudoku variant. And yes, with classic sudoku requiring 17 clues, you just have to add additional hints to make anything with 16 clues or less solvable. And a lot of variant puzzles are still a lot harder than anything you'd find in a newspaper.
There are lots of interesting patterns and strategies emerging from variants that scratch just the same logical itch as sudoku does. And sometimes ideas from variants get picked up by setters for classic sudokus, like the Phistomefel ring, which was popularized by a setter who mainly sets sudoku variant puzzles.