It just ruins an mmo.
Look what happened in Classic WoW.
People will optimise the fun out of any game if given the chance and as absurd as it may sound at first they need to be forced to have fun.
No boosting means people out there playing the game, making the world more alive, cooperating with other players and making their experience more fun, and actually having fun themselves regardless if originally they would have chosen a more ''optimal path'', the more ''convenient'' path.
Boosting means a less alive world, a world with fewer people to team up with and socialize and have fun with, lots of fresh max levels with bad gear and no clue when it comes to their character making pugging a very frustrating experience for all sides especially for the boosted fresh max-level and it means a huge boost to the illcit gold sellers and the game feeling like a p2w even if its not really.
So please make it so that parties made of higher levels + lower levels have a huge xp and item drop chance debuff.
Also, make it so that quests aren't considered done if the objective was achieved with together with a higher level (10 levels higher for example).
