I never played Pokémon but by exp share you mean the party members who are not in battle also get exp? Isn’t that a good thing?
In parts. If you played Sword and Shield you came at the gym leader with 10 or 20 levels ahead the gym battle lvl pkmns.
The old exp.share, as the name suggest, 'share' the exp with other pkmns. Is good for pokemon with high lvl train pkmns with lower lvl, but the new you can litelary beat a game without using your others pkmns because your main/others get so full exp instead of sharing some.
For me, after beating 100% this is kinda good for competitive, but let him turn ON the entire adventure broke the game. You just go to the pkmn center to refresh the PP.