The EU can't force people to switch to Mastodon. We are a democracy not China.

From what I understand this is not about forcing individuals to use one platform it another, but rather about what the official instances themselves use. And I very definitely think the people can and should force the EU to switch away from platforms like Twitter

They can encourage it though. They can mandate that all their government officials use Mastodon as their official communication channel. If you want the latest news from the government or want to communicate with government officials that’s the only channel.

No, but all EU states could use it and other Fediverse-enabled software, and mandate that all big social networks be interoperable.

The EU isn't shy of regulation.