How many has Rashford missed for you now? I think he got slightly unlucky with this one, hit the inside of the post .. could so easily have gone in and was so close to being a perfect pen. Pogba's also wasn't that bad and was a decent save from Patricio.
But overall I've always had the idea that Rashford is a decent penalty taker, has taken a couple for England and scored (one in a wc no less) and I remember the one against PSG, another very high pressure situation. I might be wrong and he's missed a few but if it's just this one or a couple then I wouldn't see any reason to think he's not good at them, even Kane's missed a couple and he's almost a guarantee from the spot.