The wormhole was a portal to the Gamma Quadrant. Everybody in the Federation would have been excited about a completely new frontier. Barring section 31 the Federation is not a secretive organization. The destruction of the Odyssey may have been classified, but if you recall DS9 at the beginning of season 3, people were leaving DS9 because it was so dangerous. If civilians knew about it, then a starship that stopped at DS9 right before being sent to the DQ would know that the Dominion exists and it is dangerous.
They just weren't '#1 threat to the Federation' at the time, so Voyager might shove them into the back of their present anxieties.