The game teaches you how to play via quests often. You will be at a disadvantage come end game by not having done all your quests.
It does -- sometimes -- but the Guildhests do an even better job of teaching.
Frequently when doing class quests it's clear that the game wants you to notice
something in order to win the battle, but won't tell you what, and will let you get frustrated as you lose over and over trying to discover it.
When I first tried a Marauder during the beta (because I wanted to see Limsa, and it was the only starting class there), I knew nothing of the tripartite DPS-healer-tank MMO system, and saw the Marauder as someone who had high defense and could dish out damage. There's a story battle (level 15, IIRC) where you have no possibility of winning unless you understand that unlike in other RPGs,
enemy enmity applies to individuals.
Once you know that, you can use the appropriate attacks and get the enemies' attention away from the people you're trying to save, but since the game never tells you about this concept (and since you've been soloing so far and wouldn't have had the chance to ever learn it by chance), you're doomed to fail that battle over and over, as I did about a dozen times.
I wish the class quests were more like the guildhests, which are pretty explicit about the concepts they're teaching. The battlewarden can be snarky and contemptuous, but it's part of the fun because he
does tell you what you need to know. You've got the one where you learn not to get aggro from too many enemies at once; the one where you leave one type of enemy alone while attacking others; the one where you have to knock down barriers and dodge AoE attacks.
Giving out rewards for doing guildhests repeatedly was a great idea, because it's an incentive for people to keep doing them and learn in short, compact sessions how to play the game. If you're still learning basic concepts while in the dungeons -- and you have every excuse to still be doing so then, because of the number of obtuse concepts that this game throws at you -- your party-mates are going to be angry and it won't be fun for anyone. This game needs to do a better job of teaching people, because it really is fun once you figure out what's going on.