Eh... No one felt chagrined at having to buy tickets to 3 films named TOY STORY, films literally about toys. I think that simply put, the appeal of a Pokemon live action film never had the width or depth fans assumed among the general audience. While many of a certain age might have played the various games or watched the show as a kid the majority kind of left it at that, something they enjoyed and did as kids. Sure, you had a good number of adults playing Pokemon Go a few years back but even if they did so regularly and had fun taking part... I suspect a lot of ironic detachment while doing so. There needed to be a much, much DEEPER connection to this IP for it to have cracked the ceiling it stopped at BO wise, I think.
And this might be a function of the franchise itself. As a story, with Pokemon... There's not a lot of "there" there, so to speak. Whatever fans feel it can be or is about... Is pretty boilerplate. "It's about friendship and working together!" Oh, really? AND? That's like... Well most every film project aimed at kids for the last 40 years. The characters are not these well developed and unique things.
It's a bit of a catch 22. You go and add depth to these things and the fanbase yells "Betrayal! You are overthinking this! It's supposed to be pure!" But if you don't do that... The general audience goes, "Ah... Another bland thing for kids. Well... Okay." There's nothing engaging or compelling as fans think there is to hook in everyone else who isn't already a die hard fan.
I feel this is similar to the Power Rangers issue. In a way, this film and the Power Rangers movie? Both felt to me like they were about as good as those two properties were ever really going to be adapted into live action. Despite the nostalgia factor... These things have never really been about anything. The appeal isn't something that translates into anything that can carry a film all that well without adding a layer of complexity that in itself goes against what fans are so enamored of in the first place. And the franchises themselves have nothing in the source that's really all that amazing in terms of storytelling or characters. Neither was something that grew into entertainments that had anything to say about anything, least of all the characters themselves. I'm not saying that they need to tackly like, real world issues or the like, or be "grim and gritty" (whatever that means as a criticism since that' something of a buzz term folk like to just throw around...) but... They have to be more than just the silly entertainments they were originally conceived as to pass muster as modern films or at least offer something more. Which is hard when A. There's not much there to work with to begin with and B. The fans will scream bloody murder whenever alterations, even needed ones, are enacted on their beloved childhood franchise.