Factual error: Blanket statement for most of the series; 90% of the tackles and blocks shown in the anime would never fly in a real soccer match. Some are particularly outrageous and deserve separate mention, but in general everyone's defense is careless at best, and downright criminal at their worst. Take Kojiro Hyuga's introduction; his 'dribbling' involves shoving the opponent off and the challenges for the ball end up with the opponents bleeding and with torn socks. Any ref would stop this sort of 'play' right away.
Factual error: During the series it's routine for powerful shoots to rip through the net. Needless to say, that can't happen with human strength. In later seasons there are shots that even leave craters in cement walls. Remember, nobody in this series has superpowers. It's supposed to be dramatic and over exaggerated in how the whole pitch feats play out, but those holes in the wall are real.