Dr Stone's characterisation.
Dr Stone is an extremely interesting animanga, the way it focuses on science and education is different from practical any other anime shonen released during the same era as it. The characters of this anime were great and enjoyable, but that's the thing they only were.
Characters become a shell of themselves as soon as they join the Kingdom of Science and this isn't the mangaka's fault in all honesty, it simply is the fact that this cast is way too big. It makes logical sense within the show for it to be a larger cast as it represent Senku's growth within the new world however in a writing sense it forces many of the characters to basically take a colourful background aesthetic. Yes, these characters have undergone their arcs but keeping them around now just dilutes their former identity as colourful noise that says the one trait that makes it stand out.
I'll use one of my favourite characters as an example, Moz. Moz is an antagonist within the third season of the anime, within the treasure island he is a hedonistic man who lives out his pleasures along with multiple women due to his overwhelming power. But he has cunning and his own code of honor which made him have a devastating fight against Hyuga during that same season, yet after he joins then what? He loses all the depth around him regarding his code of honor and battle prowess solely to become a background figure who is solely a brute like Magma who also faced this same character derailment. But then again, it isn't the mangaka's fault because you can't showcase every character's inner complexities when you have over a dozen people per episode.
Taiju, practically the original deuterogamist of the first seasons is now relegated comedic bits and nothing else-- same with Yuzuriha. Yo, one of my personal favourites, no longer is a corrupt police officer who masked his cowardice with arrogance is now just a vehicle for slapstick in the actual background.
It's like unlocking the final boss as a playable character in a video game, they just become a saturated version of what they used to be. I still do like Dr Stone, but it's like every season it feels hard to get attached to new characters like Stanley or Xeno because the same thing is going to happen to them. If Ryusui had his own movie and still got turned into a weaker version of himself, it makes me feel like there is actual no chance that anybody but Senku would have more than one personality trait by the end of the season.