The solution I've seen work is have engineers and designers that can take much of the detailed spec writing on, and have the PMs spend time with users/prospective users, partners, etc, understanding the market and users better. When you pull PMs in to all the details, often they turn into project managers, shuffling bug tickets around etc, taking time away from owning the user and the problem and shifting them too much to the solution side. Have a lead engineer own much / most of that. Every org / product is different of course.

I agree with you. The healthier organizations work in the way you mention.