It probably comes down what you expect the average new joiner experience to be.
Piefed.zip (and lemmy.zip) for instance gives the choice to the user. A message from the main .zip admin from a few weeks ago
Hey so I’m like a week behind here, but piefed.zip (and lemmy.zip) already blocks hexbear, lemmygrad, and lemmynsfw by default, and sends a PM to the user when they sign up to let them know why we do this, and how to remove it.
https://piefed.social/post/1649716/comment/9763199
I don’t know why fediverse Devs seem allergic to giving users control of their own experience.
I've seen first hand a vast majority of potential new joiners drop due the platform requiring too much configuration to be usable. I understand why some instance admin want to have "good defaults" so that new joiners would at least stay for a bit rather than saying "this whole thing is nonsense, I'll just stay on Reddit"