This is excessively reductive.

Media (social or otherwise) is a force multiplier. Ultimately it is the sensory, feedback, and control mechanism for a social system. And yes, if you change the informational behaviour of a system you fundamentally change that system's behaviour, there are still other factors at play.

Corruption, inequality, biases (themselves often reinforced through media, yes), environment, and various other endogenous and exogenous factors also come in to play. I'd also call in other informational elements, including widespread surveillance systems and AI, which operate in at least part outside the scope of social media.

That social media exacerbates many of our present problems I'd agree to. That it's fundamental to all of them, not so much.