In the books, the role of the Atreides family was not to be the good guy but the necessary evil to reach the final step of saving humanity. Even Paul can't stand his own role in the story.

Not so much opportunistic but unavoidable. He's a slave to the powers surrounding him, and the more real-world power he attains the less choice he has in how to wield it.

The real gut-punchers of how his station is betraying Paul's actually and genuinely good character are going to come in the second book, that is, subsequent movies.

And, yes, Paul, the Atreides in general, are good people. Noble, honourable, just, wise, kind, upright, everything, to a fault. Which is the only way to tear down the Messiah archetype, the Messiah has to fail despite their virtues, the failure has to be dictated on them by the universe, in a way that's not incidental but an unescapable truth about how the universe works. Or at least humanity.

I only read the books so the movie may have course corrected somewhat to make that clearer. I feel like in the books it was a little bit like greek tragedy but Paul gets the "shades of grey" treatment for much longer than he deserves.

I have to admit a bias though that since the books kind of go off the rails pretty quickly I tend to prefer to look at Dune as a stand alone work strictly from an enjoyment standpoint.