the original 6 frank herbert books occur chronologically from book 1 and are mostly Paul/Atreides-centric; this show is (I think? I haven't gotten further than book 3) partly based off of a prequel book by his son who's been writing more stories since his dad passed.
totally agree with how it doesn't feel like a good stopping point. as much as it's been cool seeing stuff from the books that didn't make the cut for the movies (the galactic origin story of the butlerian jiha- *ahem* Wars, the landsraad, space-foldin', BG school, origins of Space Hatfields vs McCoys), it's all done a disservice by how they haven't really clearly defined where the (main?!) Prophecy part of the plot is going, except for the inevitable 'book readers can guess where it eventually goes', which is uhhhh kinda lazy? and also feels like it lends itself to them working backwards from that a la lazy StarWars-style multi-TV-show Homework. is it just Max moving to 6-8 eps a season for anything vs the 10 it was back in the day? budget nonsense of 12 total vs 16 or 20? like you say, would be real juicy to know.
oddly enough, I feel like the GoT prequel show has what is probably the reverse of this pacing problem? (non-spoilers) the first season is lots of good worldbuilding AND plot and ends in a place that makes sense (and is 10 episodes), and then season 2 was (I think?) impacted by the writers' strike and is 8 episodes and ends oddly. will be interesting to see how people feel about this season once the second one eventually happens.