In the same way "software engineer" can encompass a broad spectrum of actual job functions, "product manager" can be a highly catch-all term that varies by product, seniority, company, and even personality.
In some companies, they are essentially project managers who groom the backlog and coordinate releases with support, and (ideally) take a variety of coordination tasks off of engineers plates. At the other extreme, they're pure concept+strategy, and (ideally) provide a clear vision that allows other teams to understand where they are going and allow them to prioritize independently.
There's a few other dimensions I could probably name, but wherever someone sits on these dimensions, it is possible for them to be bad at their job - either because they're a mismatch for the job they have or because they're just not very good.
This isn't unique to PMs, of course - I have worked with a lot of engineers who are bad at their job for the same reasons. And I could s/product manager/software engineer/ in the linked article and recognize a lot of the same negative behaviors and patterns.
I think one of the reasons there are a lot of bad SWEs and PMs is that roles that were once only appealing to people who were genuinely passionate about what they were doing are now considered general purpose desirable careers. When I started working in tech 25+ years ago, most of the people who were entering the software industry found computers and technology deeply interesting, and enjoyed working in the space. When product managers started to appear as a more defined job function, the best PMs were experienced engineers, marketers, etc. who cared about and understood their users, the business problems, and could help drive things forward as the landscape became increasingly complex.
Today, there are a lot of people who enter software engineering and product management who are not particularly interested in the work. It's just a job, it's just pushing bits or paperwork around, and while many of those people are still effective, it can engender the behaviors depicted in the article.
That doesn't mean the role is a mistake, especially since the article depicts the most negative version of product management: "These PMs you hire have no vision, charisma, expertise, strong beliefs, or technical skills."
That's the problem right there - the role of a product manager is fundamentally about driving clarity. That clarity could come in the form of better requirements, customer understanding, a strategic focus, and yes, even things like metrics and goals (if they are clarifying!). If a product manager is not providing clarity, they are bad at their job. If an engineering team knows with exact clarity what they should be prioritizing all the time, they don't need a PM.