I doubt most professional philosophers think of Alan Watts as "a mere entertainer," but that may partly because he is probably not widely known by professional philosophers. I have not seen his work discussed in philosophical texts (books, journals, conference papers), though I think his work deserves engagement especially when it comes to thinking about Asian philosophical traditions. Those philosophers aware of him, probably think of him as part of the counter-cultural movement (Timothy Leary, Abbie Hoffman), but I think he was a more disciplined thinker than, say, Alduous Huxley and he had a gift for making Asian thought (Taoist / Buddhist....) accessible.
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Do any professional philosophers have admiration or use for Alan Watts? Even though I have a Masters in Philosophy, I never heard of him until recently. If professionals think of him as a mere entertainer, I suppose that is fair enough, but he is a pretty good explainer.