Honestly, the "Strong Rival, Weak Rival" was such a good direction to take the series in, they just gotta emphasize on it way more.

Gen 6 sorta wanted to do this with its characters so you have various aspects of the game to compete on, but they wanted the game to be beatable by 4 year olds, so just forgot about them.

Gens 7&8 tried it again, but just didn't give a fuck about actually making them strong or weak, they just TOLD you one is struggling and the other one is dominant.

Honestly a lot of difficulty problems for the series could be solved by just having certain harder battles (against the "strong" rival, per say) where if you lose, the game just carries on.

Good players could beat this as an actual challenge, while bad players just continue with the game. You could even take it one step further and design the game to increase the difficulty a little bit with each of these "harder battles" you win, sorta like adaptable difficulty. Like what if each time you defeat the stronger rival, all the trainer pokemon in the game are 1 level higher, or beating him every time makes the elite 4 use an extra pokemon.

What do you think?