It’s a show based on the most forgettable character in the most forgettable Star Wars movie
Regardless of the general public’s knowledge on Cassian, Rogue One remains of my favourite star wars movies and Cassian has always been one of its highlights. One of the best disney star wars characters imo.
That’s your opinion, and I respect that, but I personally disagree.
Rogue One has always been one of my least favorite Star Wars movies. Beyond shallow fanservice and cool-looking shots, it has almost nothing of value to offer. It’s the only installment of the franchise that falls victim to the Eight Deadly Words: “I don’t care what happens to these people.”
And Cassian does have a fairly decent arc (although it was only made obvious with his spinoff), but I stand by my assessment that he was the most forgettable character in that movie. After watching it for the first time, I distinctly remembered the “depressed main character girl”, the “funny killer robot”, the “blind guy who fights with a stick”, and the “guy with lots of guns”, but Cassian just faded into the recesses of my memory completely.
When Andor came out, I genuinely had to assure my family that the main character of the new Star Wars show had appeared in one of the movies before, because they had forgotten him even more than I had. If that’s not proof of how forgettable Cassian was before his show turned out to be inexplicably good, I don’t know what is.