The disconnect happens because you're comparing your individual taste to a metascore -- an aggregation of other critics' reviews.
Everybody will dislike or be disappointed in something that the majority will like.
Music reviews can be very political or based on popularity of the artist(s). In gaming a very low score can almost always mean a very flawed game. In music a low score can just mean that artist didn't progress enough or wasn't what is in fashion right now.
I was surprised that their earlier albums weren't better received by critics though.
One of the weakest aspects of the album in my opinion was the utter lack of relevant situations where the album could be played. You can't play any of the tracks at a club, party, or even just casually hanging out with friends. It's an introspective, needy album, unlike Homework and Discovery.
I haven't heard any RAM tracks played anywhere after the initial Get Lucky phase wore thin.
Homework feels similar, I have a hard time just listening to the plain album. There's good stuff there, it's just too "raw". I don't have a good word.
Conversely, I'd argue that the most disappointing album was also a product of critic quirks more than anything - they vastly overrated the mopey indie rock of The Antlers during the last years where that was fashionable.
I agree though, overall the album was not that good. They were all over the map on this one.
I heard that when their following live album came out (Alive 2007) people actually started appreciating the RAM album more. Could that be a factor?