Things are setup the way they are because it’s the best way that admins (not just of lemmy instances but of major sites like reddit and facebook) have found to handle these situations.
You could take it a step further and give law enforcement their own backdoor to your site, as Facebook has done, but I would not advocate for that solution. We are in a special place in the internet where we can somewhat self-police our own content, assuming we actually self-police our own content. The way we do this is the way these admins are currently handling this.
It may be reasonable to think that sites like reddit and facebook have it all figured out, but all they have is similar code to what lemmy has, but with a bit more money to pay some content moderators on trust and safety to actually remove this content before users get a chance to see it. The difference between those sites and lemmy is $$$ and that’s not something that’s likely to change anytime soon.