They're completely different genres is the main issue. The first movie is an epic, the second is an odd coupling of political drama with romance, and while I think conceptually it's interesting it was just impossible to pull off in a Disney dtv sequel. Like the most interesting scenes had to be cut, the concept was just too dark. Also it would have so much more satisfying to see Kiara give some sort of speech because what actually happens is really non sequitur.
Although Simba is really weird in it and its hard to explain why unless you pull some major canon-welding.
Although I still like the sequel a fair amount, don't get me wrong. I just think it could have been much better executed.