Once again, there are some SPOILERS:
Like previous episodes, this one was fun to watch, but the plot was undermined by the incompetence of characters who are supposed to be smart and capable, most notably Thrawn.
For a supposed strategic genius, Thrawn constantly makes stupid mistakes. He clearly needed to study basic precepts of the Evil Overlord List!
For example, he ignores Point No. 75: "I will instruct my Legions of Terror to attack the hero en masse, instead of standing around waiting while members break off and attack one or two at a time." He could easily have wiped out the three pseudo-Jedi (Ahsoka, Sabine, and Ezra) simply by sending in his forces all at once (or even by launching one large combined air and ground attack). Instead, he sends in 2 tie fighter, then a ground force of storm troopers, then Morgan Elspeth plus zombie storm troopers, and so on. Predictably, they get defeated in detail. Ironically, Thrawn himself early on says it's important not to underestimate a single Jedi. But he does just that.
If the goal was to strand Ahsoka and friends rather than kill them, it seem obvious he could have taken off much earlier.
He also forgot Evil Overlord List No. 56: "My Legions of Terror will be trained in basic marksmanship." His troops, both air and ground, can't shoot straight to save their lives - literally! Admittedly, this is a longstanding general problem with Imperial troops, going back to the first trilogy. But a supposed strategic genius could have ordered his troops to work on this basic skill during the, ahem, TWELVE YEARS they were stranded away from home. Plus, his forces are supposed to be an elite.
Ahsoka and friends also act stupidly. They should have attacked as soon as possible, not hung out and engaged in bonding sessions, thereby giving Thrawn an opportunity to forestall them with air and ground attacks.
Ahsoka gives Sabine a pass on her incredibly stupid and irresponsible decision to hand over the map with Thrawn's coordinates to Skoll, and Sabine is nowhere near penitent enough. This further reduces my respect for both characters (but see point 11 below, for a possible non-canonical explanation for this).
Sabine suddenly has much more impressive Force abilities. There is no good explanation for this, and it conflicts with previous evidence that you need genetic talent to use the Force to this extent (which, it has previously been established, Sabine largely lacks).
Thrawn and his forces showed further incompetence by letting Ezra Bridger get away, somehow. Presumably he stole a shuttle on the Star Destroyer and took off without anyone noticing him; this highlights the laxness of their security procedures. An unauthorized shuttle launch wasn't detected (at least not till too late).
Shin and Skoll, two of the more interesting characters, got almost no airtime in the finale.
This episode again tries to highlight lessons Ahsoka learned from her master, Anakin. But they again seem either trivial ("support your apprentice"), or actually counterproductive (support her to such an extent that you end up excusing horrific errors). Also, is it really wise to follow the precepts of a man who was completely corrupted by the Dark Side and ultimately became the Darth Vader - a war criminal and mass murderer? If Ahsoka were as smart and capable as she is supposed to be, she might at least briefly consider that question.
As I have noted before, there is one highly uncanonical way to reconcile much of the above:
Maybe, far from being a great genius, Thrawn is actually so incompetent that the New Republic will be better off if he returns and takes command of the various Imperial remnants. When he does so, he will make stupid mistakes, enabling the Republic to draw the Imperials out and easily destroy them! Perhaps years in exile have rotted Thrawn's mind, and gradually turned him into a doltish shadow of his former self. Ahsoka and Sabine know this, and are actively trying to HELP Thrawn come back, as that will be better for the Republic. Plus, they get to rescue Ezra Bridger, a goal that in this scenario is no longer in conflict with protecting the Republic.
I don't want to be too negative. It was still fun to watch, and there were some cool battle scenes. The lead actors are all mostly very good. Perhaps some of the above issues will get fixed in Season 2 (assuming there is one). But, for now, I feel like Ahsoka was nowhere near as good as it should have been. And as a big fan of both the Rebels series and the Ahsoka character, I was predisposed to like this series.