I'm a developer by background. It isn't really fair to just blame it on servers/networking because the entire stack works together. Software builds on top of shared services, on top of operating system, on top of servers, on top of network, on top of the entire physical infrastructure. Bad design at the software architecture level can just be easily the problem.
I always tell my own team, before blaming hardware, server, networking, always be sure the code actually runs well in its intended environment. Just because it compiles doesn't mean it runs. Just because it runs doesn't mean it works. Just because it works on your computer doesn't mean it runs on the server. Just because it runs on the server doesn't mean it runs well. Just because it runs well on the server when you are the only one running it doesn't mean it runs well under load. All these can easily be software problems.
None of us really have a clue what's going on. Our only hope is that Square/Sony actually does. The worst case scenario is that they still don't know, and are guessing and blaming each others.
