Fang of the Sun Dougram, Armored Trooper VOTOMs, Blue Comet SPT Layzner, Gargantia on the Verdurous Planet, etc. None of these are explicitly "left wing" but you'll easily notice more pronounced elements throughout their runs.
Iron Blooded Orphans is bad, actually. S01E14-17 where Tekkadan unknowingly arm a workers uprising on a space colony and Kudelia has a little Macross moment
were great, but as far as I'm concerned that's not why most people like the show. No, they like the show because it's got a dull edge, and it's probably the first Gundam they've ever watched. Much like Gundam Wing, it's gonna age poorly, I tell you. Also, Japan's "left wing" has been associated with a loosely defined opposition to militarism and imperialism since the 1960s and 1970s. What little scholarship I've read on otaku subculture tends to point this out, often comparing and contrasting it with the Liberal-Democratic Party's longstanding desire to expand the power and capabilities of the JSDF. Indeed, Japan's "left wing" has grown even more passive with time; the fact that Hayao Miyazaki has remained the face of it in the anime industry is depressing.