Shipping a great product by itself is not enough.
That is why the best product managers do not take their job title literally. They transcend product features to focus on customer needs, company capabilities, and market realities, and to get it all done they partner with teammates like product marketing managers.
Just look at the iPhone. Not just a product, the iPhone is an evolving portfolio of programs (operations & projects) to create proprietary smartphone hardware and software, distribute it at a premium across multiple channels, and promote it effectively, all to ensure one final goal: excellent customer experience.
If the iPhone had only ever been just a product - no Apple Store, inappropriate price, no marketing, etc. - fewer of us would know about it. With less commercial success, Apple would have been forced to invest less in R&D and product innovation after releasing the iPhone in 2007. Instead of an iPhone 11 or 12, today's iPhone user might be using an iPhone 4, a Pixel, or a Blackberry.
Incidentally, there might have been a real company in 2005 or 2006 who did have a better phone prototype than Apple but never made it to market because they were missing any one of several key puzzle pieces like customer insights, good pricing, appropriate distribution, or effective marketing.
No great product stands alone. As with the iPhone and no matter your product, delivering a great customer experience takes integrated customer insights, market understanding, teamwork, and execution.