You're making a huge mistake that lots of professional writers make.
You're thinking like a "writer" and not like a "fan".
To you, as a writer going back to an element previously introduced into the series years earlier was a natural development in the series.
But to lots of fans (perhaps the majority).
The "prophets" were just one more ridiculous element of the very annoying Bajorans that lots of fans wanted forgotten.
Thus having them suddenly come from nowhere to stick their noses into the biggest story in 24th century Star Trek continuity was galling.