The way to combat this surely is for more of us driving development of service federation - W3C recently approved ActivityPub as a protocol, and Mastodon (federated micro-blogging twitter-clone ~ approx half a million users across 60 public nodes) has adopted it already. Friendica or Diaspora for federated Facebook alternatives have hundreds of thousands of users across multiple nodes globally, and they should be implementing ActivityPub (or already implement the older OStatus) in future.
Over time and with any luck, these big corporate platforms for Social Media will be weakened by the federated services. You can get your email from any provider on the planet, so I don't see why in the future your email provider couldn't offer federated social media as part of the service package. Customers could be given the ability to register on a home node for their ISP, which would then allow them to post to, and follow others' activities on nodes across the world just by using their email or federated user id.
The whole benefit I see from federated social media is that it can also tackle all these issues relating to extreme and explicit content that Facebook and Twitter have reluctance to deal with - every node owner can be more vigilant on policing content as the nodes are usually themed to a particular topic. It's likening back to the pre-social media days when discussion forums were vastly more popular, and better policed by moderators specific to the site/forum.