I am expecting a lot of Disco Elysium, here...and nothing wrong with that!
A video gaming student organization I was once part of actually had a vote on their favorite sayings. The winner was the evergreen "Perhaps the same said could be said of all religions..." from Castlevania: Symphony of the Night! https://www.youtube.com/watch?v=OMTizJemHO8
Later we had a second voting, which decided on the cult classic Trio the Punch's "BAD CHOICE"! https://youtu.be/rIPtzZHJnkg?t=454
My personal favorite? It's hard to say...but hey, that's what the scientist in Half-Life can comment, word to word! So maybe I'll put forward, said by the aforementioned: "My god, what are doing!?"
Tl;dr: Check title.
I'm more familiar with pre-20th century stuff and tend more towards musicals and opera than straight plays, but I'm a big fan of the great 18th century Bourgois revolutionary operas William Tell (Rossini) and La Muette di Portici (Auber). The first was the trigger for the 3 days in July, the latter for the Belgian Revolution.
There's also the ballad musical Reedy River, about the aftermath of the Australian 1891 Miner's strike that triggered the formation of the Australian Labour Party, the first Social Democratic Party to take power in the world.
If your looking for Socialist Operas/Plays/Ballets, the Maoist era plays (often filmed before staged, but they're all quite stagey in scripting) are better than their reputation suggests. The Red Detachment of Women is a particular favourite, though I prefer the ballet to the other adaptations.
For 20th-century straight plays, I recommend John Crawford, particularly his "Rocket Range" which examines the effect of the Woomera Rocket Range opening on local Aboriginal Communities.
Ah - the only one I really know from that era was the 1831 Spartacus - which actually with all the historical context of the time was quite bold. I got to see Il Trovatore done in the classical style a few months ago and it was also pretty amazing, even though according to my opera inclined friends the story is rubbish.
Those are all great recommendations. I was looking into old Australia the other day learning about "Swag men" so that's all up my alley.
It's a shame there's no theater com on hexbear. As much as I shit on it for being filled with libs these days, it's general disposition especially historically is very radical.
Anyway, thanks again.