Dune was always going to be a 2 parter. Just like the books, and the earlier 80s movie(not sure if there was an 80s part 2 tbh). The earlier movie was popular as it came out at the right time, was scifi-y enough as well as being not terrible. Plus at the time was a high point of scifi/fantasy movies.
I enjoyed the first book, but it is somewhat predictable. Obviously the protag boy is the messiah, there is no doubt about that. Haven't watched the new one yet. Or the old one for that matter. Will get around to seeing them both eventually.