Just finished it (spoilers)
The plot is quite weak, it relies heavily on mythology and emotional manipulation.
The northern tribes Glossu could not handle suddenly just not a problem, simply because Feyd-Rautha took over, who was sort of a sword fighting junkie with no governing experience.
After finding out Paul was alive, why did the emperor just have to go to Dune? Isn't the spice production already restored?
Paul Atreides once captured the emperor, could simply take over the empire? The great houses would just stand down?
The emperor said he had to terminate house Atreides, because the Duke was weak, that makes no sense. Why would he want a strong lord who could challenge his power?
I guess the justice system was still about duels, it looked like to punish or dethrone the emperor Paul just had to risk his life in a duel, even he has already taken everyone prisoners?
And how would Paul being a Harkonnen has anything to do with his ascension to the throne? Harkonnens could not do it themselves and he destroyed Harkonnens.
Maybe someone who has read the books could connect those dots, I just felt it was a bit puzzling and ridiculous.