If no one listens to you, who is a formal education valuable to, exactly? I assign no personal value to the pieces of paper I got from the various institutions I've graduated from - society and the job market values them.
No, you didn't. You said you don't assign any value to the piece of paper. Find, but did you actually learn anything in the process? That has value, to you.
Now, perhaps your point is that the formal education didn't matter, that is, you could just as easily have learned the same thing by informal means. That is true, if you had the self-discipline or curiosity to do so. While you may have had that, and I did, many who attend public school do not. The things they learn are still of value to them.
I can understand the sentiment well enough. The person holding the sign has the impression that experts in epidemiology aren't being listened to by some people. But their education is still very much in play and is clearly valuable, so I don't think the sign is really making a useful point. It's just complaining.