Finally after months of me complaining, the management team has gotten the approval to hire one additional developer who has experience with API development. To be honest though, I am skeptical if one developer is going to change anything, and I can imagine that a lot of skilled developers won't be staying here long when they see that we don't really have the personnel in place to deliver on the vision that the management team has set.
I definitely am not a people manager (nor do I want to be again, been there done that), but I can imagine that our engineering manager is in a tough place right now too. A lot of the development team are close to retirement age and he can't really push them too much due to the fear of them leaving and taking their years or decades of domain knowledge with them.