Spider-Man's superhuman abilities and precognition overwhelm Cap's peak-human fighting skill.
This is the same fundamental matchup as Batman vs. Spider-Man โ peak human vs. enhanced superhuman. Cap is physically stronger than Batman (super-soldier serum vs. peak training), but Spider-Man still outclasses him.
Peter can lift 10 tons vs. Cap's 1,200 pounds. Spider-sense nullifies Cap's shield throws and tactical surprises. Peter's webbing can immobilize Cap and neutralize his shield.
Cap's vibranium shield is a better defensive tool than anything Batman has, and his super-soldier endurance exceeds Batman's. But the fundamental problem is the same: Peter is too strong, too fast, and has too much precognition for a peak-human-plus to overcome consistently.
Cap's shield absorbs all kinetic force and is an offensive weapon Peter must respect. His tactical mind and super-soldier serum make him the best human-tier fighter in Marvel. He's fought Spider-Man in the comics and held his own through skill.
Spider-Man is 8x stronger, significantly faster, and has precognition. Web-shooters can immobilize Cap or his shield. Peter is nearly as smart as Tony Stark and can out-think Cap tactically while overpowering him physically.
Spider-Man wins in most encounters through superhuman physical advantages. Cap's shield and skill make this closer than most superhuman-vs-human fights, but Peter's stats are simply too superior.
Captain America also fights
Spider-Man also fights