No, it doesn't need to change, that's what the problem is; it did change. Pokemon post-Gen 2 (G/S/C) is decidedly different in both tone and art style. Not that Pokemon was ever mature, but it was grittier like most things from the 90's kids were into. You'd be hard pressed to find any cartoon for kids as twisted as Ren & Stimpy, any video game as epic and competitive as Pokemon, or any animated dramas with as much quality writing, music, and animation as Batman: The Animated Series and Spider-Man '94. Opinions like this are written off as each generation claims its was better, but the 90's and early 00's were objectively superior.

What is Pokemon now? Diabetes sweet friendships have replaced spiteful, tense rivalries, and they doubled down on the "love your Pokemon" concept to the point where it far over shadows the journey to be the best. Newer games just feel empty and cartoony. Team Rocket seemed like a real threat and were based more closely on mafia than later teams with their ridiculous goals.

At least they released Pokemon Red/Blue on VC recently...

I enjoyed both Rush games, I did think the action was sometimes too fast to see what was coming up in terms of hazards though, which meant replaying the same stage a bunch of times, other than that they were enjoyable, good special stages, 3D sections and bosses for the most part.

DS is one of the best consoles of all time. Such a rich library of software
Zelda were all glorious on it.