See, I don't think the movie needed more Pennywise. It probably has as much Pennywise as the first film did, if not more. To me the issue comes with how repetitive the movie is (both internally and when it comes to the first film), while not having much to actually say.
One of the big problems with how they divided up the movie, is that they basically told the character arcs in the first film. So what you have here is a bunch of characters who don't have arcs. The movie is strangely super exposition based. Rarely stops with the exposition. This is why I think they needed to bring in elements from the book they ignored. Flashbacks shouldn't have been such a large part of this film. Moments? Yeah. A big chunk of the movie? They served no narrative purpose that could not have been told in the present. It just adds runtime.
Also an easy way to make it different from the first would have been making this film not just about Pennywise, but Derry itself. The realization that it is more then the clown.