As a huge Pokémon fan, I have mixed feelings about this.
As a detective movie (cauz, y'know, the movie is called... Detective Pikachu?) this is probably the dumbest, poorly-written plot I've seen in a while. The link that leads each scene to another is often so weak, it feels like they made a movie out of the trailer. Too much things happens "because the plot said so", like the characters motivations changing so quickly it becomes unconvincing, or very important technology that's not being introduced or foreshadowed before it's used with or against the characters, at a point it makes the movie extremely unsatisfying at times. Actually it's so bad, it turns into a guilty pleasure. But at least, it's straight-forward and good-looking enough that anyone can understand what's going on, even a little kid who's never been introduced to Pokémon before.
Combined with its solid visuals (the CGI team made an amazing job at making Pokémon characters look believable in a live-action, which in itself is a miracle) and its great humor (mostly thanks to Ryan Reynold's performance), it's overall a pretty good entertainment that will please your nostalgia or that your kids can enjoy, as long as you don't expect anything creative, thoughtful or challenging out of it.
It's a Pokémon movie we're talking about.