Dune is soft sci fi. TBP is hard sci fi. They're very different formats of stories. Good hard SF generally doesn't have character development. In fact character development is a kind of subgenre called bildungsroman. I don't know why ppl these days expect characters to change as though it's some inherent part of a book. Some books are thought experiments or about world building. Part of reading for me is to try experiencing something novel. But on your hate for TBP, I'd say the huge fanbase, the Hugo committee and Obama would disagree with you on that one.
I don't "hate" TBP, so not sure why you chose this characterization. I just find it overrated. When I finished the trilogy, I wished I'd have gotten back the hours I spent reading it. That's neither the mark of a good book nor a good writer. And let's not pretend that the Hugo committee is some sort of arbiter of truth. Plenty of real stinkers (N. K. Jemisin anyone?) have won it.
Also, If I'm in the mood for hard sci-fi, I'll read Peter Watts who is (again) on a different league. Blindsight and Echopraxia navigate similar (but not only!) themes to TBP in a much more intelligent, thought-provoking and cohesive way.
I'm considering start reading TBP. So my question to you is why did you progress through the trilogy if you find it kind of substandard? Meaning, once you are done with first or even the second book what made you consider reading the next books in the trilogy?
This is an honest question as someone who is seriously considering reading TBP in near future.
Because enough people I know were raving and kept telling me it starts slow / payoff comes later. Well, I won't be listening to these folks again re: books that's for sure!
If you're dead-set on reading it, read the first book and if you don't like it cut your losses short right there. I say skip the whole mess and read Watts instead.