What "open exploring" is in Dawnguard? As great as it is, if you take away the Vampire Lord and Werewolf Perk Trees, then you have crossbows, a few new locations and a couple of quests.
Are they well made? Yes they are. And is it fun and worth having? Of course it is.
But in terms of new material, Dawnguard has very little. In that mod, everything is made from scratch, new models, new textures, they all come together to make something unique. Dawnguard does not have this, it uses pretty much the same meshes and textures from the vanilla game. The complaint from many is that it's just "more Skyrim".
That's fine of course, and doesn't mean you have to have custom resources for something to be good, but to say it has more variety than that mod is wrong.
Well yes, if you start removing features from consideration, then you obviously end up with less. What Dawnguard provides is two new perk trees, a new type of beast form, new NPCs, new items, new spells, two new questlines, etc. etc.
And in terms of "from-scratch", Dawnguard has a number of totally new item designs, as well as new enemies (not re-textures), the vampire lord form, and new spell effects. To say nothing of the two new questlines and all the unique locations that have been added for them. And it integrates into the open world (there are new radiant events, new locations, etc.) instead of in its own module.
Again, Moonpath is phenomenal. It's wonderful. It's free. But you can only compare one or two features to a professionally-designed DLC before it starts to lag behind.
http://skyrim.nexusmods.com/mods/8429
Until now 57 voidced NPCs, everone with more dialogue and personality then any NPC of Skyrim.
And again, if all the modders are focusing on is voicing some new NPCs, then you can't really compare it to an expansion-sized DLC that has all the above features.
People seem to think that it's insulting to modders to say that their products aren't at a professional level. It isn't.