These people need to stop crying about the new system. It is like a baby crying because of new blankets. As Chris Christie said, "If you don't like it, then you don't have to do it". Except instead of doing, it is playing.
That's not really fair. Fans of this series have been waiting for a long time for this game to be released, and if there are features that outright ruin their ability to enjoy the game then that waiting becomes pointless and they're left with no alternative (since, for better or for worse, nobody really makes this sort of game except Bethesda).
EDIT:
^^ Usually they're the same
Not really, no. Steamlining's a term that's often used for most anything that makes a game easier and smoother to play or interact with, whether that means removing things, changing things, tweaking things, or outright replacing things. It doesn't mean an inherent and total loss.
Dumbing down, on the other hand, is mainly a term people use to describe changes they don't like when they have no specific criticism to bring to the table.