A correct slippery slope identification is when someone says "A happened, thus Z will happen." That's a stretch. But "A happened, then B, C, D, E, F, and G... Z is looking more likely", its no longer a slippery slope. Its a valid concern. The slope is slippery and we're falling down it. The first case can still be right, even if we only had one data point at the time. Its incorrect to assert it is absolutely right, but its also incorrect to dismiss it just because there's only one data point.
Slippery Slopes are, absolutely, among the weakest logical fallacies to be proven wrong by internet armchair warriors with the Fallacies wikipedia page open in another tab. We can make the easy jump all the way to Goodwin's Law and assert that it is a known historical fact that people in 1930s Germany felt the same thing as these armchair warriors when the Socialists were drug away. And then the trade unionists. And then the Gypsies. And the Jewish population. And tens of millions of good people were killed. Slippery Slopes are absolutely a real thing. Having a fallacy named after them doesn't mean they don't exist.