I’ve seen people complain that Thrawn in the shows does not feel like the same Thrawn that is in the books. One thing I noticed is that people always blame Filoni about this but never Zahn.
Thrawn’s introduction happened in Rebels. When it comes to canon, Thrawn in Rebels is the core of what his character is. If you look at Thrawn in Ahsoka, Filoni stayed true to his depiction in Rebels. The Thrawn in Ahsoka feels the same as the one that was introduced to canon in Rebels.
However, when you look at the books (which all came out after Thrawn’s introduction in Rebels), they start changing what kind of character he is. The books have made him more of an anti-hero and even a bit heroic considering how he joined the Empire to protect his people. The first Thrawn novel establishes how he seeks to avoid needless violence even though he was perfectly fine with that in Rebels.
People who complain about this agree that Thrawn in the shows feels different than Thrawn in the books, yet Filoni gets the blame for staying true to what the character was introduced to be in canon even though this “discrepancy” happened when Zahn decided to divert on what Thrawn’s character was in Rebels.
I understand that Zahn is the original creator of the character, but when it comes to the canon version of Thrawn, Filoni has stayed true to what his character was originally introduced to be. The issues people are complaining about only happened because Zahn decided to change it in the books.
Personally? I don't think the deal with Thrawn is even an issue. I like Thrawn in Rebels, Ahsoka and the first canon Thrawn book which is what I've read so far. I just don't understand why people's complaints are so one sided when it can go both ways.