Quick join will put you into game modes that are bad for new players:
a) they’re maps that aren’t fully finished yet, so there are many exploits that the better players will use against you.
b) the game mode doesn’t display Dirty Bomb in its best light - the Objective and Stopwatch modes make the game a truly unique and fun experience, rather than just another game using the CS:GO gamemode in a slightly less polished way.
c) the execution game mode is far less forgiving - if you die you don’t respawn, so it’s not great for new players who are still learning the mechanics.
d) you get more XP and credits from the other gamemodes.
e) the starting mercs are pretty terrible for execution - Aura is terrible on the grass/rubble map (can’t remember the name) due to her close-combat playstyle, while Skyhammer’s airstrikes are pretty limited on Market since there are rooves everywhere.
I do see the concept that new players will adjust more quickly to Execution as it is a common game mode among FPS games, but to be honest Objective mode is really easy to learn (as long as you play the tutorial).
Please, Splash Damage - make the Quick Join favour Objective gamemodes first, then Stopwatch and LASTLY Execution.