Have seen this brought up quite a few times, but in recent years the only publicised departures have been people in marketing and social media roles, either leaving – yes – because Konami working culture is terrible or seemingly for reasons of career progression. I mean really, who has there been? From memory: Asim (think he quite clearly was frustrated with the company and how they treated him), Adam (promotion to a larger, less PES-specific role), that Lennibo guy (could easily be career progression), Lygaard (only ever a behind the scenes marketing guy), who else?
And how do we know these roles aren't being fulfilled/rehired?
In short, I don't know how much to make of that stuff. It doesn't scream an exodus of development talent or anything. I do think Konami probably has a toxic working environment, especially when we think of public-facing roles, and that it has sounded like from prior reports the communication between Japan and Europe isn't great. But I'm not sure any of this directly reflects on the development side.
Is it though? I don't know yet what to conclude on the basis of that beta. But by contrast, a lot of people have been decrying the lack of skilled developers in the Konami PES team for the past 5 or 6 years. Is anything newly bad?
If the quality of the final product is as underwhelming as the beta, another issue could be limited personnel, or development priorities being dictated from the top in ways that don't benefit gameplay (get the hair right, make sure you have this stadium looking great, etc.).
I don't know what can really be inferred about the development team.