I would call that more like a post-WoW MMO than a "standard" MMO. What you complain about is what older styles of MMOs are like, which emphasized freedom and exploring more than following the linear playground they set up for you.
GW2 is kind of a mix of both old and new. The quests and events are a lot more playground-like than old MMOs, but they encourage you to play your own way and explore like older MMOs.
Personally, I've not had much trouble feeling I'm under-leveled to progress in PVE, but for a caveat here's the pattern I seem to have fallen into:
Enter zone
Begin sweeping for heart locations, check if nearby dynamic events are too stiff for my current level
Do the first few hearts
Be sure to hit all points of interest, challenges, and vistas along the way
Also harvest everything from all three categories, not just the one I'm focusing on crafting with
Take random breaks during this time to warp back to home base and perform crafting with a focus on discovery
Pay attention to my progress with the daily achievements and hop around to a few places in zones I've already been in order to take part in random events that are running and kill a variety of mobs.
So... isn't the leveling balanced to take crafting into account? It seems they really want to encourage people to craft here, especially with the bonus XP from discovering, and the fact that the gear you craft for yourself can actually be really great at any given level range.
It does seem the game is 'old school' in how it leans towards expecting the player to occupy themselves by figuring out what they can do, and to be fair to that design choice it's very free in allowing you to focus on what you really feel like doing at the moment. Also unless I'm misunderstanding it, going back to previous zones to clean up dailies and participate in random events in progress still gets you good XP and good rewards due to how the level scaling is set up.
Rather than move from zone to zone and have each previous zone become irrelevant as you progress towards 80, to me it feels like what is really happening is the game world is opening up more and more. The entire thing is your playground, and earlier areas do not become irrelevant or useless for progression.