Mostly agreed, but as an employee you do have some semblance of material non-public information that gives you a structural edge in assessing the stock. (This probably works better at a 1k-5k company than a Google/FB, but I can't say because I haven't worked at the big faangs).

I've benefited financially from having a good sense of how well things are going and holding/selling accordingly (within the confines of the law and blackout periods, of course).