Not all attractions are built to the same standard of "Immersion", even these days. This one is a bit more self-contained than any of the Galaxy's Edge or Pandora attractions, and the land around the Chinese Theater isn't necessarily designed to communicate what you'll now find inside.
It's also possible that the imagineers felt in this particular case that this attraction would need to be more heavily advertised than the new signless trend would permit. Assuming that their aspiration was ultimately that this be another attraction with no incongruent signage, which is not necessarily the case.
Let's also consider that there are attractions with signage that doesn't make perfect thematic sense who would still suffer if that signage were lost. The Haunted Mansion comes to mind - it's a thematic masterpiece, but has anyone ever really felt it would be much better off if they got rid of those Gate Plaques? They don't make sense in-world, but they do valuable work for the experience.
There's more than one way to skin a cat, as it were.
Part of me does wonder if there was a way this sign could say "Perfect Picnic" and then somehow "break" and flash Runaway Railway, telling the truth of the ride while still staying "in-theme" for the story, kind of like the Hollywood Tower Hotel/Tower of Terror sign. That could have been fun and covered both bases. But I don't hate what this ended up being.