They are good arguments as long as you can show evidence the slope is slippery. The slippery slope fallacy isn't that slippery slopes don't exist, it is that they are asserted without evidence.
Showing that you can get n+3 via separate evidence for n+1, n+2, and n+3 says nothing about n+7
Slippery slope arguments would need entire dissertations of evidence to even be plausibly considered, and yet they’re one of the most common methods of naysaying.
While you’re technically correct, I’m functionally correct.