This film was inherently a failure. The very basic rule is that you do not meddle with OT main characters. On top of that, you simply cannot do a Han Solo film without Harrison Ford. And even if they used a time machine to make Ford young again, the film would still suck as the very basic rule is broken.
The only thing that is inherently wrong with this film is that it’s a story that doesn’t need to be told. However, that doesn’t mean it can’t be told well.