The Introduction of a party-wide XP share destroys any aspect of training your team. Leveling your team used to take thought and strategy. Now any moron with a type advantage can steamroll an entire section of the game and the rest of their team gains levels without even participating. That's not challenging, that's intended laziness. There's not even an option to turn off XP share (UNLESS YOU PLAY X/Y, BUT THE GAME NEVER NOTIFIES YOU OF THE OPTION IN THE KEY ITEMS POCKET OF YOUR BAG). If there was a difficulty option with XP share on AND off, i wouldn't have a problem with it. It forces you to think critically about your party and their stats (even though a large % pay no attention to their pokemon's EV/IVS anyway). I digress, as of sword/shield, there's absolutely no way of turning off XP share. Its hard baked into the loop now.
I never understand why people say xp share makes pokemon too easy and takes away challenge when the games are already easy af to begin with and XP share literally just makes the game way less grindy which is a good thing tbh