Firstly, this won't be a fix for everyone. Network environments these days are very complex and there will never be a one size fits all type of fix. I'm sharing this as it really improved my experience with PES at first, but then I noticed improvements in friends list loading and BF4 and some other games. It might not work for you, but the more things we try, the more focus we might bring to the actual problem.
What it does not improve: This didn't seem to make a difference to PSN message slowness and/or 'could not find opponent' message. It did seem to have a positive impact on general matchmaking though. It also seemed to 'reduce' the stutter in single player though not eradicate it.
Environment: My PS4 is wired into my Virgin Superhub.
My symptoms: I seemed to be behind everyone online by a second. My players seem to react slower, and the opponent was already in the process of closing me down before my player had received the ball. It felt like I couldn't compete because my PS4 was not keeping up with what was actually happening. My record before trying this was 1W, 3D and about 7L. I made this change yesterday and went to 2W, 1D and 0L. The all round experience was night and day as well. Not only was I competing I was actually able to create chances!
Changing your MTU: So what i did was change my MTU on my PS4. Default it is set to 1500, which was the same as my router. To detect your optimal MTU, drop to a command prompt and do the following:
ping google.com -f -l
xxxx
where
xxxx is a number. You want the highest number that does not fragment. Might take you a little while to find the exact number. Here's an image example:
NOTE: You could also look at your router's MTU size and knock 28 off it. For some reason the 28 byte header seems to be the key value here.
Next you need to go to your PS4 network settings. Select 'Set up network connection' or whatever it's called. Choose a 'Custom' setup. Accept all automatic settings until MTU. Set this manually to the value you discovered above (or your router's MTU - 28). MTU is usually an instant change but I like to reboot things anyway to reload the network stack etc.
Log into PES, get a game and see if the actual in-game experience improves (forget matchmaking for now), and report back here to say it worked or it didn't work. Give it 5 games or so to get a general 'feel' for it as well.
Why does it work? Not sure, as I said environments are quite complex. Perhaps there's something strange if PS4 MTU matches router MTU. Maybe PSN is better at dealing with non-fragmented packets. Maybe the overhead on 1500 byte packets is too much at PSN end (volume/processing ratio) or there's a config anomaly. This is all pure speculation and to be honest I don't care as long as I can play games smoothly. I suspect those buying new routers have a different MTU size on their router and it has indirectly resolved their issues.
Hope it helps some, it not all people anyway. And please remember to report back so we can gauge if it is quite a reliable change to make!