if they weren't doing such a disservice to the idea of skepticism.
They do hijack "skepticism" the same way parascience hijacks "scientificity". They just borrow its terminology and its varnish, and ditch any methodology that goes against their targeted conclusions.
Science is already, by definition, a methodology of critical, skeptical open-mindedness. It's how it functions and progresses, in all its fields. It's how it sorts out the verifiable, the refutable, the scientific object, from the unverifiable and non-refutable metaphysical belief (the circular logic of faith, etc), and that's how it drops what turns out hogwash. Parascientists complain that scientists show "no curiosity" about telekinesis or ectoplasms, or that their "fear the truth", but, like electricity in early 19th century (or black matter nowadays), any unknown natural force would have fascinated scientists if there was actually something to investigate. In reality, it's parascientists that are terrified of facing the void of their obsessions.
Likewise, all skeptical movements (of the James Randi kind) start with how to debunk idiotic conspiracy theories, cultist propaganda and scams of that ilk, no matter the source. Skepticism is alive and kicking, you don't get mainstream parascience stars ŕ la Uri Geller anymore, the bermuda triangle is now just a folkloric joke, and so is the Loch Ness monster. But conspiracy theorists (often encouraged for political motives) keep using the skeptical lexicon like they'd use a stolen lab coat, without applying or understanding any of the related methods. They play pretend. And they don't harm skepticism more than skeptics harm them :
http://skepdic.com/tifraud.html
I'm not anxious for skepticism, and I really don't think these wackos have any adverse effect on it. There's always frauds, lies, official narratives and fake news to debunk, and they do get debunked regardless of the fringe deliriums that mimic their format to push a (self-serving or ideological) narrative - and that get debunked in turn.
For whatever genuine, there will always be cheap impostors trying to pass for it. Conspiracy theorists are just the vaguely parasitic background noise of skepticism.