Except the real experts in the field don't think much of him. Part of being validated is having the respect of your peers. That's why it's so easy to toss out the opinions of rogue antivax scientists.
What's interesting about Taleb is that given his takes on GMOs and "naive interventionism" he seems to have been advocating quite strongly for COVID vaccination against people that have tried to use his ideas to argue against it.
It would have been so easy for him to use "antifragility" to follow so many other pubic intellectuals who saw an opportunity to promote their "heterodox" brand and gather followers advocating for natural immunity and other remedies.