Dull is not a word I would use to describe it. That is how I would describe Fallout 3 and Fallout New Vegas. I would describe Fallout 4 as engaging.
Yes, there are less real choices in the dialogue itself and no science or perception checks, but we don't live in a perfect world where I always get what I want. In fact, I rarely ever get what I want... But Fallout 4 delivered.
I can't understate how much of an improvement it is to have short options as opposed to long readouts on the dialogue interface.
It is a brilliant artistic choice that improves the pace of the game and makes it easier to stay in character. If I am playing a character that is a real 'Goody Two Shoes' and always does the right thing, then I don't want to have to read through a sarcastic option that says, 'Oh, I would totally love to get shot up by mutants for you' or a mean option that says, 'I don't have time to help your hole in the ground settlement, you are probably just going to die anyways'. That kind of stuff throws you out of the character that you are in.
And then when I do play a second playthrough, if the game is like New Vegas and has everything written out on the screen, then I already know everything my sarcastic jerk character is going to say, because I had to read it when I was playing a goody two shoes character... No surprise, so why even play the game a second time when everything was shown to me the first time.
The sarcasm option is great, because it is always a surprise, it wouldn't be fun if I always read it first.
Yes, it would have been great if Bethesda had more choices in the same way it would have been great if my car had more horsepower. Doesn't mean my car isn't great for the price I payed, but it is just something I would always like more of no matter how much I got.
I will still take Fallout 4's dialogue that is totally engaging over New Vega's dialogue that is lifeless and feels like someone is just talking 'at' you and not carrying on a conversation 'with' you. Yes, New Vegas has a lot of false depth with its dead end conversation options that mostly just abruptly end things. But I don't look at having more ways of missing content to be a real improvement, and I don't think all their paper thin factions with 1 or 2 missions really means the game has more role playing ability, as still only 4 of the factions had any real meat to them.