Deep Space 9 is probably the most radical thing I’ve seen on television. There’s Space Palestine, they directly quote Marx, and whenever they tackle a social topic it’s so far ahead of its time. Only the CGI feels dated and even then it holds up well.

edit: Also the rule of thumb with any Star Trek series is to endure the first season when they’re finding their footing. DS9 starts out feeling like a 1990s sitcom, but by S2 the writers have really found the ideological core of it.