Dungeons you just get dungeon tokens and though you can get vanilla legendary parts with them... it is mainly just exotics and no ascended.
This puts it at a less desirable point then things like fractals that can give ascended and are shorter.
This is simple so far but here is where it becomes a problem....
WVW reward tracks... You can get everything from wvw.
Ascended gear equal to that in fractals.
You can even get map completion achievement skins.
The problem is that you can get everything from wvw and really...... with boosters...... in many cases it is faster. Especially things like Map Mastery Achievements for the lws3 skins or dungeon loot. This is because of reward tracks.
This reduces the amount that will actually do things by map achievements, dungeons, and even fractals since you can get ascended from wvw also.
The other game types do not offer ALL of this and only certain parts instead.
Such as fractals not giving a way to get dungeon loot or map achievements skins.
The only point in wvw that is in a gray zone is the hero point tokens. Seeing as people in wvw that are mainly pvp players should have the ability to get there elite specs.
However why can people in doing mainly pvp gameplay get everything from pve? Giving them the hero point tokens is one thing because they need them. However giving them things that should req achievements in zones from lws3? If people want pve focused things then go play pve.
It is not like dungeon, fractal, or open world event focused people have a reward track to get all the pvp stuff like the backpacks and skins.
WVW and the reward tracks are just far too giving compared to other areas of the game.
Also though not advised and just creates dead weight for a wvw zerg.... you can technically just run around with a zerg mashing 1 and get the reward tracks completed and tons of wvw tokens. As I said... not advised and it is looked down on because you are just dead weight. However the fact you CAN do it means you can in fact get say.... the skin given from the map mastery achievement for ember isle can be gained by just by mashing 1 in wvw. Now compare this to actually doing the achievement for the skin. Do you see the problem?
Most will not if given the choice do 2-5x more work for the same reward. It is a issue of reward vs work that makes other game types like dungeons feel so dead.