Well, aside from the fact that people expect the "block" function to block the blocked user, and not merely mute the blocked user...
"People dislike change." Coming from any other platform, they expect the "block" feature to work the same way it did all their lives. When they find out it doesn't, they will feel that kbin breaks the established norm of reddit, mastodon, twitter, instagram, facebook, every messaging client, and every other site with a "block" feature, constitutes an unannounced and unwelcomed change from every other service, and not only leave, but carry and share strong negative opinions about the fediverse.
Maybe having the fediverse not being janky garbage software would be better?