Yes, Polanyi was not a Marxist, and literally nobody would say he was. He had distanced himself from Marxism at a personal level after an initial flirtation with it in his youth. Polanyi turned away from Marxism in the years leading up to the First World War.

Certainly, he was somewhat of a socialist, though his theory differed significantly from Marxism. His theory revolved around conflict, similar to Marx's theory; however, the terms, dynamics, and mechanisms were all distinct. Upon rereading "The Great Transformation," it becomes clear that the second Karl (Polanyi) had deviated considerably from the first Karl's (Marx) fundamental insights on various critical points: the emergence of capitalism, the origins of the Industrial Revolution, the dialectics of commodification, the exploitation of labor, concepts of value and money, class power, and class struggle.

Some Marxist authors were indeed inspired by Polanyi, as with the already mentioned Burawoy, Nancy Fraser, etc. However, that doesn't retroactively make Polanyi a Marxist. Aside from that, Polanyi was very religious; he converted to Protestantism and remained a Christian for the rest of his life. He leaned much more towards being "communitarian" than "communist".

edit: https://sandbroo.faculty.politics.utoronto.ca/why-polanyi-and-not-marx/ here's a text with a better explanation.