You are right, most people on the far left (i'd say two third of them, maybe it changed in the last ten years) would say that participating in elections is supporting the institutions and the dominant class.

But right now radical left == far left for most. Worse, right now in France, a lot of people really think the reformist left is the far left, and the rest believe they are radicals. Saner, but still wrong. This is mindblowing, but i am not a professional historian or political scientist so it doesn't really matter to me, i won't loose any sleep. It just says a lot about how low our political culture fell. They aren't even anticapitalists nor they push for worker ownership. And i've read today that the overton window was pushed to the left?

One thing still that can explain this: it seems that the 19th century history lessons were erased from our western memories. And even the years between WW1 and WW2 are not that clear for western europeans.