I actually disagree for several reasons.

One is that activitypub is an open protocol. It's for the individual servers to decide who they want to federate with, not some centralized decision made by an authority of the fediverse.

Another is that there are many good reasons to have more people, and especially casual users, entering the fediverse. Artists could share their work on Pixelfed, where they are the rightful owners of their own accounts, and yet have it shared with mass audiences including Threads users. For many people, this is essential for making a living doing what they do.

Other people who don't need to (or want to) have that kind of reach can be on servers that federate with the artists, but block Threads users. They'll see what the artists post, but they'll remain oblivious to the comments made by Threads users.