I don't find scoring to be an issue but it all depends on game length, game speed, difficulty level, and to a lesser extent, tactics.
I'm pretty amateur when it comes to soccer games so I started PES 2017 on normal level, 9 minutes, and the fastest game speed. Playing ML mode I started in Italy div 2 and did pretty well with many 1-0 or 2-1 games which is pretty realistic. I took a contract offer with Levante in Spanish div 2 and had to bump things up to PRO because they were the best team in that division. I've only scored more than 3 goals a few times despite dominating the league and winning the division title. Most of my scores were 2-0 or something.
I got promoted to div 1 and was still doing so well that I now play on Top Player. Scoring isn't consistent as I have several 0-0 games recently but I also managed to beat Barcelona 3-1 and one of the weakest teams in the division 5-0. Honestly, I only buy and play a soccer game every couple years so this feels like quite an accomplishment for me.
Try to keep in mind that scoring more than 3 goals a game is a LOT of goals. I know it can be frustrating at times when all your shots miss or hit the post and you end up with 0-0 scores or 1-0 losses, but that's soccer for ya.