I think people have warmed up to it over the years, but the chorus of "Kid B-Sides" comments when it released was resounding. Which is odd to me since it sounds nothing like Kid A at all.
I remember when it came out and that sentiment was definitely there simply because it released six months after Kid A and was recorded during the same studio sessions. Some of the songs had been heard during the Kid A release. Pitchfork's review of the record even claimed the b-sides thing... while giving it a 9/10. The album objectively reviews better than a good deal of their releases.
i wouldn't say it was maligned for it, it simply was a great album that was a victim of its own circumstances of being released so close to a record that was both a radical departure and beloved.