Sorry, but missing 15 games when you're an 8th grader is not going to impact your kids soccer "pathway", maybe if they're sitting on their butt playing video games for 3 months it might impact them, but even that's doubtful. Kids play too many games as it is and do far too little cross training. Part of the problem with US youth soccer is the hyper focus on game play with too many games. Between league play, showcases and tournaments its absurd how many games kids play. This is also one of the primary causes of burnout, and between 8 and 9th grade is when it is mostly likely to happen (although it's not always burnout, sometimes its just better options).
Again what your experiencing is FOMO. Use the time off to your kids advantage. Go snowboarding on weekends, have your kid learn how to ollie a skateboard, take them to the pump track with their bike, organize pickup games with other "trapped" players, do speed and strength training.