It really isn’t that slop didn’t exist before.
It is that it is increasingly becoming indistinguishable from not-slop.
There is a different bar of believability for each of us. None of us are always right when we make a judgement. But the cues to making good calls without digging are drying up.
And it won’t be long before every fake event has fake support for diggers to find. That will increase the time investment for anyone trying to figure things out.
It isn’t the same staying the same. Nothing has ever stayed the same. “Staying the same” isn’t a thing in nature and hasn’t been the trend in human history.
True for videos, but not true for any type of "text claim", which were already plenty 10 years ago and they were already hard to fight (think: misquoting people, strangely referring to science article, dubiously interpreting facts, etc.).
But I would claim that "trusting blindly" was much more common hundreds of years ago than it is now, so we might make some progress in fact.
If people learn to be more skeptical (because at some point they might get that things can be fake) it might even be a gain. The transition period can be dangerous though, as always.