I highly agree with much of what has been said and would add that Product Marketing is a pretty ambiguous role when you think about it. It is often very different according to the org. Tranferring to a new team or having a new boss or a new CMO could mean an entirely new idea of what Product Marketing should or shouldn't be doing and what success looks like.
For example, in one of my experiences Product Marketing was nearly 100% product strategy and organizing (like a Project Management Office) product launch, with zero focus on content, demand generation, etc. In my role now Product Marketing is 100% responsible for all bottom-of-funnel content, be it landing pages, ads, sales or channel material. I am now bringing the team to the strategy table with product.
What I do is create a "Product Marketing Strategy and Metrics" doc and align that with every important stakeholder in the business, everyone on my team and new leaders so that we understand exactly what everyone is expected to be delivering and measured on.