In the way you are using the words “direct social agenda” as a structured plan to transform society, there are none i know of. However, things do not have to be either white or black. The training in sila is an integral part of the Buddhist path, and the whole purpose of morality, in a way, is to organize the relationship between the individual and others.
In Buddhism, there are teachings for lay people which addresses the relationship with the family, with partner, issues of integrity at work, what constitutes a good friend, on the virtues of generosity, gratitude …etc. There are also rules organizing the relationship between monastics and lay people.
There are also the four brahma viharas. Mental and emotional developments are not two separate things in Buddhism, at least as i understand it.
Social media are supposed to be neutral platforms for their users. They do have certain rules to cover themselves legally and to regulate the platforms they manage, but they have no ethical teachings to offer. Big difference!
So, its not only about impact, but about intention. The intention of the teachings is to end suffering.
While the scholarly approach to the texts is a disciplined one, it comes at an expense in my opinion. For example, you wont find a sutta that indicates a social agenda, and yet, one would be naive thinking that the Buddha did not know that the well being of the individual and the world affect each other. He had to design his message to the individual though, and sometimes encourages him/her to seek solitude even, for good reasons. And yet, seeking a sutta that explicitly states a social agenda, and making this as a criteria to measure the Buddhist intentional impact on society is an oversimplification in my opinion.
And who knows to what extent this rigid/dry approach to the texts led to the emergence of later teachings which emphasized selflessness and activism and making it even THE ideal!
Finally, i don’t disagree that the OP question is valid, but we seem to have different approaches to answering it.