Why not contact Odo?

You know the first thing Picard & friends should have done after finding out Changelings were involved in this conspiracy, is contacted Federation Space Station Deep Space 9, get in touch with Kira Nerys, who in turn would head through the wormhole to the Gamma Quadrant and seek out Odo at the Great Link (Dominion Homeworld), to find out if he would be able to help with the situation.

I know actor Rene Auberjonois has since passed away--rest in peace, but there would have been alternative ways to bring back the character and it would have been awesome to see Nana Visitor back as Kira. At the very least, bring back Doctor Bashir or Chief O'Brien, as their expertise with Changelings would have been exactly what was needed for Picard & friends.

Where it stands right now, the entire Deep Space Nine crew (minus Worf) is completely absent from this season of Picard, yet they would be the ones most relevant to handling the Changeling threat. I guess there are a few episodes left for some surprises, but we'll see...