Slowly making changes is a normal strategy at this point, saying anything less than the worst case is a "slippery slope" is no longer relevant imo. It is a valid risk that should at the very least be a point of discussion
If your ancestors managed to survive in the natural environment, and there is something novel in the synthetic environment, then the synthetic alternative does in fact deserve more scrutiny because you have less evidence about it.
"Natural doesn't mean safe" type reasoning only really applies when the natural and synthetic thing are being put in equally novel situations--which is a pretty rare setup. Like, how often do you consider eating a plant which nobody has ever eaten before?
Do you mean that an argument which consists of a claim of an inevitable slide to a bad conclusion from a certain starting point is your pet peeve? Or that a rebuttal to such an argument, which consists of pointing out that the former may be a slippery slope fallacy, is your pet peeve? It gets confusing because the key phrase of the former is "we're on a slippery slope", while the key phrase of the latter is "that's a slippery slope fallacy."
The logical fallacy still holds even if the majority of all policy utilizes the incremental strategy, but only because there are edge cases that invalidate the argument.
The problem for people outside of the strategy room, is that we don't know whether there is a broader objective or not, and even when a broader objective is realized it's almost impossible to prove that the end result was the original intent.
Even absent a broader objective we should still look to history and understand that government only ever increases its own power, only ever reduces the liberty of the citizen.
Government actions move in one direction, to yell into the void "well that is a slippery slope fallacy" as if that means we should simply ignore all of the lessons history has to teach us about giving up liberty for perceived safety is crazy to me.
I am not sure what value there is in proclaiming a slippery slope fallacy or how that it a rebuttal to the very real historical record.
In some cases, folks are open about their broader objectives. Sometimes, we DO know their broader objectives, or at least we COULD know if it was widely (properly) reported.
In all other cases, we have no way of knowing the objectives of politicians and bureaucrats _tomorrow_, so we shouldn't presume they will have good objectives -- or rather, that we would think their objectives Good.
Never give the government power that you wouldn't want the most hostile political adversary to have.