The whole point of a team is to compensate for the individual's limits in ability or attention.
True, but a team is rarely much better than the worst of its members . . . You can't just throw people together, call them a "team", and expect outcomes to improve. Individual skills have to learned, and teamwork has to be learned, too -- how best to support and/or fill in for people. During the learning process, mistakes WILL be made and should be expected. The SEALS don't throw their green recruits into high-stress operations, because they know that.
Once again, this should be FUN. Practice should be fun . . . if it starts feeling onerous, go do something else (carve pumpkins ). Yes, there will be dives when people are discouraged with their performances. Those are the days when part of the teamwork is to buoy up the discouraged person. Cheerful, motivated people, put in a learning-conducive environment and offered opportunities for practice WILL learn. Discouraged, apprehensive, tense people will continue to make mistakes and become self-fulfilling prophecies.