I missed out on a lot of communication for my kids' extracurriculars because they were only on Facebook and I don't use it. It's infuriating, but less infuriating than the other platforms that a couple of the groups used to attempt to communicate schedules and requirements.
It's ridiculous that this sort of thing isn't a solved problem. Schools need to communicate with parents in an effective way, yet none of the platforms I've used work well. I've been in tech for decades and I still have trouble with their shitty UI.