Bingowings said:
It didn't deserve a cinema release
I think that was the main reason for being so badly recieved. It was not made for cinema, it wasn't "the 7th Star Wars movie", and most reviews didn't realized it was a pilot for a TV series. Hence the surprise to many when they saw the premiere of the series.
But yes, the movie wasn't so bad. I enjoyed both Christophsis and Jabba's Palace parts. And they got Christopher Lee, so that's a plus.