Every time something like this gets posted, there are always Lemmy users crying to defederate their Lemmy instances.
But remember, the current concern is with Mastodon, NOT Lemmy. Lemmy can’t actually view the post types that Masto and Threads make. Wendy’s can post all the Threads ads they want - we’re not going to see them here. We can’t. That hasn’t been built.
Try it. Go view someone’s Mastodon account in Lemmy. You don’t see their posts.