I just saw Star Trek Enterprise Season 4 Episode 18: ‘In A Mirror Darkly’ and I noticed that someone that looks vaguely like Karl Marx leads the mob to raid the Vulcan ship.
Also on another note … what the hell kind of fever dream did the writers drift into with this side story that lasted a few episodes? They just come out of left field for no apparent reason.
VOY had a similar problem. Tried the Kazon, the Vidiians, the Hirogen, a few one-offs, and then back to the Borg once the Queen concept had been established. The main goal of reaching home over such a distance left them leaving behind any credible ongoing threats. Why else create the transwarp network if only to allow the Borg to become a consistent nuisance?