I'm reminded of Bret Victor's recent comment on reading Latour:

It’s tempting to judge what you read: "I agree with these statements, and I disagree with those." However, a great thinker who has spent decades on an unusual line of thought cannot induce their context into your head in a few pages. It’s almost certainly the case that you don’t fully understand their statements. Instead, you can say: "I have now learned that there exists a worldview in which all of these statements are consistent." And if it feels worthwhile, you can make a genuine effort to understand that entire worldview. You don't have to adopt it. Just make it available to yourself, so you can make connections to it when it's needed.

That, to me, is a principle of charity well applied. I wouldn't at all say that steelmanning is a stronger form of that -- a rationalist trying to steelman Latour would be like your Roman trying to steelman progressivism. Steelmanning is about constructing what you see as stronger versions of an argument, while the principle of charity is about trying to get into your interlocutor's head under the assumption that whatever they're saying or doing seems reasonable and right to them. The latter is much harder and rarer, in my experience, although that's not to say the former isn't more valuable in some situations.

You describe some real problems with steelmen. I think a first-order defense against them is just to ask whether your interlocutor agrees with your steelman or not.