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This paper contains a nice summary of Gödel's interactions with Russell. https://www.cambridge.org/core/services/aop-cambridge-core/c...
Gödel's future work on constructible hierarchies and the dialectica interpretation were directly inspired by Principia Mathematica. I agree that characterizing Gödel's view on Principia as a "step backwards" is overly simplistic, but he certainly mentions and takes inspiration form the work throughout his career.
> as he was mainly criticizing the syntax
If you mean to say that Gödel's criticisms of Principia were just about syntax - that is also incorrect. Gödel had substantial complaints about the truthfulness of the axiom of reducibility that (IIRC) Russell himself thought posed a valid attack on the system in Principia.