There's certainly a lot of areas where PMs can improve, be it prioritisation, stakeholder management, and execution skills. But all these things can be learned, honed, and taught - and a lot of the time that depends on the type of leader you have. I've worked with leadership that only care about PMs "delivering" on things (purely output) and not to worry about vision and decision-making. This is what then leads to the lack of skills, imho. It's not like I woke up one day and just "knew" how to be a product person. I had fantastic people that taught me (and keep teaching me) along the way!