Actually I'd say before the recent buffs most people thought DKs were a little weak and could use some help (including me). Now most people think DKs are fine and that it's about time DKs stop constantly crying.
You don't have large burst damage. As an unholy dk you spread diseases around and usually end up topping the meters in overall dmg, while having strong defensive cooldowns and decent peels. If you don't like that game design then re-roll a class with strong burst. You're never going to have both.
Not exactly. Some started to admit that DK's needed help, but whenever we brought up the fact that DK's were weak and needed this buff, or that buff, we were told "OH IT WILL BE SEASON FIVE ALL OVER AGAIN" - even in the case of completely reasonable changes (such as the unholy blight disease cleansing blocker that came in 3.3.3).
Basically, as long as we said nothing we needed help but whenever conversation actually started we would get flooded by people who are amazingly still butthurt over season 5 saying that DKs are still overpowered or are fine. This demographic was largely rogues/mages/priests, and it continues to this day.
And you honestly expect people to reroll after possibly making DK's their new main and spending a lot of time and effort on it? No class is a utility class, no class is a support class. These are just apologetic terms people give to shit classes. Every class brings both damage and utility or healing and utility.
The utility card that people play whenever DK's are discussed is overused and exagerrated. When you see classes like mages, hunters, warlocks, warriors having the damage that they do along with their utility (two polymorphs or two fears in a row has the same effect as every single DK cooldown chained into eachother) and then you see death knights, you see a gap in design.