"This works really well when the engineers themselves have all the knowledge+ability to tackle the problem."
This reminds me of a similar situation almost a decade ago where someone watched a talk on how GitHub uses GitHub to build GitHub. The people who watched the talk all tried to convince me that we should adopt similar process that puts less emphasis on PMs. However, this worked for GitHub because their engineers had such a strong similarity to their customer base. For us that wasn't the case at all and we typically needed PMs to have lots of customer conversations and explain to us how customers used our product because we were building Enterprise software for people whose day-to-day we didn't understand easily.
This reminds me of a similar situation almost a decade ago where someone watched a talk on how GitHub uses GitHub to build GitHub. The people who watched the talk all tried to convince me that we should adopt similar process that puts less emphasis on PMs. However, this worked for GitHub because their engineers had such a strong similarity to their customer base. For us that wasn't the case at all and we typically needed PMs to have lots of customer conversations and explain to us how customers used our product because we were building Enterprise software for people whose day-to-day we didn't understand easily.