I really like what I have seen with PICARD season 3 thus far. At the very least, 4 episodes in and it hasn't taken a nosedive, unlike the previous seasons, and it feels like a more cohesive story is being presented.
That said, there are still 6 episodes left, so I can't fairly judge the season until it's complete.
And even if the season turns out to end great, it is still just one season under his belt. Calling someone 'the greatest showrunner for STAR TREK' or words to that effect... shouldn't they do at least two seasons before being given such a title? Just to prove that what they did wasn't a fluke or just lucky or a 'right place, right time' situation.
All of my favorite showrunners from various shows (in and out of ST) have had more than one season under their belt as a showrunner, except for Manny Coto... and that's really only because he didn't get the chance to continue past ENT season 4.
So while I respect that a petition for Terry Matalas to be the showrunner for the next series is an nice idea for fans of his work (and I really loved 12 MONKEYS, it's definitely worth watching), at the end of the day, the studios will not hire a showrunner based on petitions from a fanbase. Petitions may help create a series or prevent a series from getting the axe because it does show interest, but that's a far cry from hiring someone to handle all the day to day production issues. Showrunning is much more than being able to tell good stories and guide other writers in the room. Some people are better at writing episodes than showrunning, and vice versa.
A good example of this would be Rick Berman... whether you agree with a lot of his decisions or not, he kept the franchise going for 13 years after Roddenberry's death, not to mention he basically took over in the last couple years he was alive. So he knew how to run the business. But he was not a very good writer.
On the flip side, there's Jeri Taylor. I think she is a wonderful writer... just look at some of her episodes. "The Drumhead", "The Outcast", "EYE OF THE NEEDLE", "PERSISTENCE OF VISION", "ALLIANCES", "NOTHING HUMAN"... she wrote very, very strong episodes. But as a showrunner, she quite honestly fell flat... the two seasons she was the sole showrunner, TNG season 7 and VOYAGER season 3, were the weakest of both shows.