My nine year old started watching this movie today... she wasn't terribly engaged by it. :/
I guess because much of the appeal is for fans of the OT ... it kinda runs off the power of nostalgic references and if those references don't mean much then I suppose it's not so entertaining. She did seem more interested when Han met Chewbacca, because obviously she knows who Chewbacca is. But many of the more subtle references just flew over her head.
Rogue One is also a fan's movie, but she knows enough about Star Wars to enjoy that. I guess because Rogue One only requires you to have basic knowledge of the movies, whereas Solo requires more in-depth knowledge like the significance of the dice, the significance of the blaster, what a Crime Syndicate is yada yada yada. But even for fans who know this stuff it's like, I get it but still meh.
As
the Honest Trailer says, not everything needs an explanation!