So hypothetically you are suggesting that someone like Nigel Farage or the Brexit Party could just file DMCA requests against any YouTuber who has made a video critical of them, and YouTube and Reddit would have to suspend the accounts because they're at the mercy of DMCA?

If that were true how come this isn't happening all the time? I know it happens often, but not universally. It seems like this is the easiest way of killing dissent and criticism. How come the folks who have the most criticism levelled against them haven't figured out this tactic if the law is so flawed? How is it that it only happens in some cases but not others? If the law is broken why doesn't everyone exploit it?

I suspect that you are right that DMCA is a flawed law but I think in this particular case there may be more to it than just these companies being at the mercy of a broken law.