Boring mathematicians of the school of actual concrete formalisations level the criticism that his Principle of Computational Equivalence is never given a formal definitive statement and is more of an aspirational feel good kind of fuzzy wuzzy thingy.

eg: Lawrence Gray in his 12 page review: https://www.ams.org/notices/200302/fea-gray.pdf

Cosma Shalizi's infamous Rare Blend of Monster Raving Egomania and Utter Batshit Insanity review: http://bactra.org/reviews/wolfram/