Honestly? We can probably just say this is all Francis the Chameleon’s fault.
http://www.nintendoworldreport.com/editorial/42883/e3-2016-divergent-paths-throw-paper-mario-and-mario-n-luigi-into-no-win-situations
At E3 2016, Nintendo showed off Paper Mario: Color Splash, due out on October 7 on Wii U. The Treehouse Live demo confirmed what most figured: this wasn’t a secret sequel to Thousand-Year Door’s RPG stylings. Instead, it’s a card-based follow-up to Paper Mario: Sticker Star. When Color Splash hits later this year, the non-RPG Paper Mario games will outnumber the RPG ones.
Both the Paper Mario and the Mario & Luigi series are stuck between a rock and a hard place. On one hand, the Mario & Luigi series is in a rut in which each successive RPG seems to disappoint large swaths of the audience despite retaining the same general flow and experience. With each entry, there’s a feeling of "oh this again?" even if the games are still ultimately enjoyable and fun.
On the other hand, the Paper Mario series didn't sit still. After a pair of by-the-book RPGs on the Nintendo 64 and GameCube, the series took a left turn with the platforming/RPG fusion of Super Paper Mario. After that, Sticker Star on the 3DS altered the formula so much that "RPG" isn’t really an applicable genre any more. It’s far more of an adventure game that just happens to have turn-based battles sometimes, and that seems to disappoint large swaths of the audience.
Most concerns about each series could be flipped around to be facts about the other. "I wish Paper Mario would just be an RPG!" Mario & Luigi has been an RPG for five entries over 15 years. "I wish Mario & Luigi would evolve more and change it up!" Paper Mario consistently went in crazy new directions in the past decade.
Hearing Nintendo Producer Risa Tabata explain why Paper Mario is no longer a traditional RPG because Mario & Luigi occupies that space makes sense, even if it’s somewhat disheartening to hear. It also lines up with what Nintendo’s Kensuke Tanabe said in an Iwata Asks around Sticker Star’s launch: "With regard to the story, we did a survey over the Super Paper Mario game in Club Nintendo, and not even 1% said the story was interesting."
If you got feedback like that, wouldn’t you excise the story from a series? Shigeru Miyamoto gets flack for Sticker Star, as apparently it was his directive and recommendation to remove the story, but following the response to Super Paper Mario, which was oft lambasted for being way too wordy, wouldn’t trimming the fat make sense?
In the case of the Paper Mario series, Nintendo and developer Intelligent Systems seemed to directly listen to fans, taking Club Nintendo survey responses to heart. Sticker Star might not have been for everyone, but it was the result of feedback and the desire to keep a series interesting. Maybe Color Splash will fine-tune that concept. Maybe it will be more of the same? We’ll find out for sure soon enough.
And that’s where we’re at with Paper Mario - the fat has been trimmed but in the process, a lot of the vim and vigor of the earlier games has been replaced by Toads, hide and seek, and acid-tripping fire extinguishers. Whether that makes it a better game or not is all personal preference, but we’re certainly far, far away from the days of the Rogueport, the Glitz Pit, and the X-Nauts.