Positivity thinking and action gets Positive outcomes.
I think some people are less... diplomatic in the way they've chosen to express their disappointments, but I don't think they're wrong for feeling that way.
When I first started playing Skyrim, I didn't care about vampirism, because it seemed largely worthless to me. Then I picked up a copy of Immortal Blood, and I was just overwhelmed with thoughts of how awesome vampires could have been. Could being the key word. Bethesda had an amazing idea for vampires at the ready, and they opted to discard it in favor of adding a few tassels to the vampires from Oblivion and calling it good.
Then Dawnguard was announced, and we learned it was going to be vampire centric. Those of us who were disappointed with vampires were equally hopeful and cautious, because we had been burnt before. When we saw the trailer and the Vampire Lord form, many of us felt disappointed that once again the lore we wanted to see come to life was being abandoned for the sake of territory previously treaded upon, maybe not in this series, but with several vampire movies and the like. However, our fears were lessened somewhat when a Bethesda staff member assured us that we wouldn't be disappointed, and even hinted that lore abiding Volkihar would be seen at last. Then, at E3, we were told that the regular vampires were receiving an overhaul. Many of us were excited that these vampires would be the Volkihar we felt should have been in Skyrim to begin with were going to be here at last.
Then Dawnguard was released, and those of us who hadn't been in the Beta learned what the "overhaul" really was: simple nerfing. The weaknesses were reduced, they received no new abilities (nor was their unique spell, Vampire Drain, enhanced), and now they weren't even attacked at Stage 4, despite the fact that feeding was easier than ever. We could no longer be discovered and hated for being a vampire, even though we now had eyes that could act as lighthouses in their own right. To make things even worse from a lore perspective, vampires that should be of the Cyrodiilic variety weren't fixed so that they were Cyrodiilic, and because of their glowing eyes the error is now impossible not to notice unless you're uninitiated.
But to me, the biggest failing is that the Vampire Lords and the vanilla vampires are the same save the ability to transform. That's all that separates the two, and it is without a doubt, one of the worst design decisions I've ever heard of. It makes the original vampires completely pointless to play as. From a gameplay perspective, they're utterly worthless, and from a story telling one, the decision seems to be made only to justify not having to come up with an actual new strain of vampirism.
To me, this whole thing kind of seems like getting the wrong order in a restaurant. You're disappointed, and you tell the waiter what happened. They apologize, and tell you they'll fix the problem in just a few minutes. So you wait, eagerly anticipating getting the stuff you actually wanted the first time around. But when the waiter comes back, it's still not what you ordered, and then you find out they're charging you for both items.
Granted, this is a video game, and Bethesda shouldn't be forced to make a game to our exact specifications, but I don't see the wisdom in these design choices. First of all, not everyone likes vampires, so making a vampire-centric DLC is a risky move. However, there are many people who are fans of TES who love the vampire lore, and want to play as those vampires, so what's the logic in making the vampires completely unappealing to your core vampire fanbase? They still didn't make playing as regular vampires enjoyable. In fact, they did the opposite, because the regular vampires are redundant when you can have all their powers plus the ability to transform at no extra cost to your character.
I'm not saying Bethesda shouldn't have made the Vampire Lords. They seem interesting, and I'm sure I could have fun playing as them, but they shouldn't have tried to connect them with the original vampires and clumsily try and connect them to the lore. It doesn't work, and it makes things less appealing overall to me and many others. We shouldn't be lighting torches and grabbing pitchforks, but we need to let our displeasure be heard, so that we can at least try to persuade them to change it. That's why this thread exists.