It changes the way people play the game and, as someone who interacts with others in an MMO that forces me to change the way I play the game.
Example, with dual spec everyone can solo farm quests and such with ease - so people like me who like to play a preferred spec and group up for open world stuff won’t be able to find anyone to join us because it’ll be easier to switch specs and solo.
It will make it more efficient and faster to do quests solo and earn gold meaning objectives will be met faster meaning there will be less to do faster and there will be more raid logging.
You mentioned you raid log because of dual spec. Fair enough but I can’t see why. You still need to do the same content and you claim without dual spec it takes you longer to do - so it doesn’t add up. I have no doubt you raid log - everyone is now, but that’s due to sluggish content release. Dual spec stands to make that worse not better.