Wolfram's problem is mindset IMO. There's a certain kind of highly intelligent mind, but because of fame, money, habit or personality, makes them intellectually lazy. Instead of doing the proofs, research, careful discussion and reconceptualizing that leads to useful theories and conclusion, they jump straight to the end, because they think they're smart. This produces some impressive sounding theory, but which upon closer inspection proves to be to be too vague to actually be testable, if not contain outright errors. People I put in this group including Wolfram and his computational theories, Langan and his Cognitive Theoretical model of the Universe, and the Italian school of algebraic geometry. There's a kind of interesting perception here. A reasonable person thinks one who makes correct theories is an intelligent man. Others think they are intelligent, so therefore their theories are correct.

My impression is different: I think Wolfram is hard-working, but his internal mental life is so full of fantasies of unlimited success and fame that he cannot manage an impartial-enough evaluation of his own work output.

"your impression", is true only in the Ruliad. Ask people who knew him back in the 80's... he never worked on anything on his own that has amounted to anything. He is a real life crank, crackpot and all around charlatan.

Mathematica is the product of 30 years of work on Macsyma and Maple systems at MIT and elsewhere, which he cracked its codebase, usurped and sold to an unsuspecting academic community back when only the likes of Bill Gates would do such as thing.

He also missed the entire LLM wave because he refused to open source WolframAlpha codebase and work with others in the NLP community.

So, ah, my "full of fantasies of unlimited success and fame" was not derogatory enough for your tastes, then?

any specific source ? (fire time I hear that about Wolfram )

My impression is based on hearing him speak for a few hours and maybe some biographical facts such as can be gotten from Wikipedia.