I've never understood this complaint. Almost all special effects are obvious, because they depict things that aren't real. I don't remember watching Ghostbusters in the theater and wondering if those were really ghosts.
Some people just cannot (or refuse to) recognise all the noise you can see around old/cheap/low quality effects. I often watched those silly Japanese horror varieties where they would show you a grainy video of some dark place, and then maybe a grainy shot of someone crawling out of something. But you know it's two separate things spliced together because the grains are of a different size, or when one area is gray-scale while another is simply decolourised to match. My friends could never tell the difference.