Terry Eagleton thinks so.

But it seems to me that there is a peril in looking holistically at historical leftists (by which I mean choosing the most radical points in their careers as representative), and comparing that to this particular moment in contemporary artists' careers (when, as he points out, many of them have succumbed in middle or age to a dilution of their former radicalism), particularly when this moment is so defined by fear and terrorism.

The point that he is making is about established, mainstream individual artists (along the lines of a Morris or a Shaw in other time periods). But of course in every age a lot of innovation and dissent will occur at the fringes of the artistic community, among the unsung and avant garde. Furthermore, it seems to me that there is a strong vein of protest in British theatre right now (although it is perhaps less polemic than the radicalism Eagleton is looking for, as the dialogic nature of the form allows), but it is being produced not by individuals but by collectives. Think, for instance, of the work done in the Tribunal theatre project at the Tricycle, which takes documentary evidence about current events (my favorite was about British residents being held in violation of habeas corpus at Guantanamo) and reworks it for the stage.