I think the point being made here is not that incels/PUAs fail to suggest some malaise, but that they reveal little of depth about said malaise, and probably better suggest the internet's ability to foster/amplify niche subcultures. The pick up artist community online is way weirder than your average college degenerate. It has complex rules and definitions and techniques and celebrities and etc. No way that exists without the internet.
Surely the term niche here is just the conceited haughty male (usually male) who looks down from olympian heights and could never deign to hold himself accountable and think actually, y'know, I'm not far removed from tibiriusincelistan1314?