1. Recurring characters.

Movies in general get away with this better than multi season shows with actors contracts and killing off a character early.

Sean Bean humourously being killed off in LOTR and Game of Thrones. This also ties into later seasons when the writers were afraid to kill lead characters. Jack Reacher does well not bringing back 2 of the leads from season 1.

Foundation is deathly afraid of this, having 6 characters that carry over season to season where in the books there are none.

2. Faithfulness to source material.

For people who have not read the books, Dune part 2 does end with a white saviour story and includes holy war, religious imagery. The distance from 9/11 helps though the middle eastern conflicts don't. A few actions scenes and techy stuff is added and some ideas and scenes are moved around. The daringness to commit to the source material is amazing, weird worm bile, talking babies, drugs and hallucinations

Foundation ignores this, having pacifist characters shoot at each other, adding pointless sex and action scenes that have no impact on the plot. The core premise abandoned very early on. It's like they wanted to make their own sci fi show but just slapped the name on it