But... isn't that the point of 538? Throw all the polls on a pile, and out of all the noise and outliers you get a good average result that might actually reflect reality. We love to hate on 538 in here, which I find a bit petty.
When all you're getting are bad polls (landline only, IVR, etc.) from partisan firms it's going to knock your model out of whack. Especially when they treat them like pretty much everything else. If you look around the various national and state polls on their site, you can see shitty polls getting heavy weight all over the place. That's a great way to generate an outlierish model.