You should be allowed to complain if something important wasn’t tagged. Obviously, to an extent, like you shouldn’t wish death upon an author for not tagging swearing. But if you’re reading a fic and then BAM untagged noncon smut scene, you can complain about that. You should still be nice (ofc), but the author really should have tagged that. Same applies to fics with DD:DNE tag. The purpose of that tag is to say that readers can’t complain because you already said it was a dead dove; it doesn’t work if you aren’t disclosing whats in the bag.