I, personally, don't consider LessWrong a cult (I lurk the blog, and have even been to an ACX meetup). There's definitely a very insular core community, though, which regularly gets caught up in "cults of personality". Yudkowski is the most obvious person to point to here, but Leverage Research is the best example of cult behaviour coming out of LessWrong and the EA community IMO.

With regards to machine learning in particular, there's some very extreme views about the mid/long term prospects of AI. Yudkowski himself explicitly believes humanity is doomed, and AI will takeover the world within our lifetimes.