It's not only that he has no academic credentials, he also has no accomplishments in the field. He has no relevant peer reviewed publications (in mainstream venues; of course he publishes stuff under his own institutions. I don't consider those peer reviewed). Even if you're skeptical about academia and only care about practical achievements... Yudkowsky is also not a businessman/engineer who built something. He doesn't actually work with AI, he hasn't built anything tangible, he just speaks about alignment in the most vague terms possible.

At best -- if one is feeling generous -- you could say he is a "philosopher of AI"... and not a very good one, but that's just my opinion.

Eliezer looks to me like a scifi fan who theorizes a lot, instead of a scientist. So why do (some) people pay any credence to his opinions on AI? He's not a subject matter expert!