One person who does it "correctly" does not wipe away all the others that don't.Sorry, but how is my sorcerer working to join a paladin order and finally making it not story based? Or making a pact with an eldritch god in desperation? Without dynamic multiclassing we lose that kind of character evolution. Not even subclasses are a proper substitute, because 1) they happen at set levels, which most of the time won't align with the plot 2) they are set in stone once taken, you only get one, and once the level where you pick one comes, you cannot change paths. This is what I call the "Reformed assassin problem". Having an assassin that doesn't want to kill anymore and wants to turn a new leaf, but due to not having dynamic multiclassing can only get better at killing people and can never learn anything that isn't dictated by that choice at first-third level. The whole setup is extremely inflexible, and demands I sacrifice my individual character narrative in favor of a platonic one that somehow would be better despite being a white room creation that is always the same despite what actually transpires in-game?

Believe me... I wouldn't bring up the point if I ever saw comments on the boards here about all Fighter / Druid multiclasses that were occurring, or Barbarian / Monk multiclasses, or Cleric / Wizards. But we rarely if ever do. The only times I ever see people commenting on multiclasses (either positively or negatively or asking for advice) always seem to be in regards to Sorcedins, Bardlocks, Bardadins, Sorlocks etc. All the ones which just happen to all be the four CHA primary classes, all of which just happen to have the most synergy and power gain because of the mechanical abilities matching up as a result.
Look, I'm as much on your side as possible... I wish everything in the game was narratively motivated rather than mechanically. But I know that's just not the way it is. You might be the one that does it the way I'd like it do be... but so long as you're one out of thousands that don't, you'd end up being the unfortunately casualty if I ever got my way.
But in truth, that isn't anything you'll ever actually have worry about, because I know full well I'm never going to GET my way. LOL. Multiclassing isn't ever going to be removed, so you'll be able to continue playing the way you wish (and which I appreciate), and I'll just have to continue to find a lot of what I see on these boards a bit bleh. But that's fine... this game isn't for me alone so I can't actually get mad about it.
