I wasn't a huge fan of Morgan Elsbeth's backstory in Tales of the Empire. I enjoyed Grand Admiral Thrawn's cameo, but there could've been so much more to his appearance in the show.
If half the series had focused on Grand Admiral Thrawn's backstory and his vision for the galaxy instead of Barriss Offee and the other half had been about Morgan, then it would've tied their stories and motives together nicely. Even though Timothy Zahn's novels focus on Grand Admiral Thrawn and a major character in Star Wars Rebels, that doesn't guarantee that everyone has read the books and watched every series.
That doesn't mean that Filoni should assume that Star Wars fans are lazy and don't know the background of these characters. Dave Filoni assumes, and rightly so, that Star Wars fans are very knowledgeable. However, this is also a fandom that's always growing, and new fans get added to the fandom with the addition of every new piece of media.
It could be that Tales of the Empire is the first time many fans saw Grand Admiral Thrawn. In that case, it would've been a good idea to provide a little summary of his history. It's a good way to draw the attention of new fans who just started watching Star Wars and don't know much about these characters.
Hopefully, Season 2 of Ahsoka will spend a good amount of time on Grand Admiral Thrawn and introduce him to fans who don't watch the animated shows and may not have read the novels. All is not lost though. At least Tales of the Empire shows us how Morgan Elsbeth and Thrawn met and why he accepted her offer to work for the Empire. They both have a higher purpose than others who work for the Empire and are brilliant in their ways. Who knows, maybe the next 'Tales' anthology series will be about the history of Grand Admiral Thrawn.
Tales of the Empire is streaming on Disney+.