LW used to be politically neutral; I'm not sure it is so anymore.

I reckon LW's more politically neutral (in kilobug's apparent sense) now than it was in 2014, but that that's mainly attributable to the fall in traffic. (I'd guess LW's less politically-neutral-in-the-apparent-kilobug-sense than I felt it was in 2013.)

(I also think that as I understand the term "politically neutral", LW was never politically neutral, because the idea of a politically neutral institution is probably incoherent in the first place. I upvoted kilobug anyway because I think they mean something else by "politically neutral", and in any case I agree with the rest of their comment.)

And the current wave of populist, nationalistic, libertarian/individualist ideology which seems to be very popular in the USA is being represented in the general atmosphere of LW.

LW's always had a big, big libertarian/individualist streak. In the first survey back in '09, a plurality (45%) called themselves libertarians. That's actually been diluted over the years as more conventional left-wingers have drifted in.