The more you like the fantastic Wreck-It Ralph, the less you'll like Ralph Breaks the Internet. And it's a shame, because a Wreck-It Ralph sequel could have been great; it certainly has a ton of potential in the characters, setting, and possible plots (potential that the fandom has seized upon and written excellent sequels themselves).
But RBTI manages to disappoint on every level, and by all accounts of unused concepts, it's a failure of Disney's meddling rather than the intentions of the hardworking creative team. The movie leans way too hard on a "how do you do, fellow kids?" mentality with tortured unfunny meme references for the sake of references, gives more screentime to forced Disney cameos than to half of the returning main cast (Felix and Calhoun were given a babysitting plot of all things in the final revision, which was entirely cut late in development and they consequently have almost zero screentime), and introduces close to ten new characters who all barely get to do anything.
Ralph and Vanellope behave in extremely out-of-character ways. In contrast to the first movie admirably avoiding this trope, Ralph here plays into the "big bumbling oaf" stereotype and is made manchild-like, with almost a little brother relation to Vanellope rather than an older sibling or father figure as he was before. Vanellope herself does a complete 180 and suddenly doesn't care about Sugar Rush anymore, and the story treats her as blameless for virtually everything that happens. Felix and Calhoun, as mentioned, have almost no involvement with the movie despite logic dictating that the whole Core Four found family would go to the internet together, and instead get reduced to an offscreen joke plot that does nothing with them as characters or their relationship other than "well they are married, therefore they have to have a babysitting plot".
In contrast to how much attention was paid to minor details in the first movie, here there are continuity errors all over the place, and the main story's resolution completely violates a huge established arcade rule that kicked off the entire plot of the original movie. Without spoiling too much, the main conflict has a very obvious potential solution given how the character selection in Sugar Rush works, but this is completely ignored and the resolution leaves the audience scratching their heads.
It's really sad that a true all-ages movie like Wreck-It Ralph ended up with a sequel that feels like it's talking down to even preschoolers. It seems as though Disney wanted a "best friend has to move away" plot, but forced it on a setting and group of characters where it wasn't workable, requiring the movie's world to be warped to fit it (not surprising that director Rich Moore left the company after this). And it's even sadder that people try to mindlessly excuse all of this by pretending that anything which isn't violent enough to exclude children from the audience should have lower quality expectations, in spite of all the movie's issues having nothing to do with its content rating.