For the majority of large, well-federated instances, I don't think it's meaningless, because deletions also propagate to other instances.

If a mod on one server doesn't like something I say, and they delete my comment, all the other (well-behaved) federated instances will also delete my comment.

Of course this also creates problems in the other direction, like servers that ignore deletion requests.

That combined with a large amount of blocked instances across the board, I feel like you get into this "which direction would you like to piss into the wind" situation where you have no idea how many people/instances will actually see your message if at all.