Just this week my kids basketball coach is trying get all the parents to "use the app" for scheduling and announcements and its just NOT working so back to email which works for everyone.
As both a player and in the past as a coach, my experience with "sports team apps" has been that nobody wants to be the end user's IT department and on any team with more than X players the odds of someone's phone being messed up approaches 100%. "Oh I have an android and you have an iphone so I can't help you" and its just infinite headaches.
If you could find a way to "do the sports team app" thing but over multiple incompatible messenger chatbots or over a web page it might get more traction.
If apps "just worked", which they certainly do not, it would be nice. An app-like experience over a web page might work.
Just use email and/or text messaging.
So if you're one of the minority of parents smart enough to import a calendar into their google (or other) calendar, they can get the game schedule there, but the less competent (to put it nicely) can continue to get a stream of emails or even plain old text messages of upcoming games. Or they could join a FB group or a different platform.
Or there's people out there whom could never handle installing or using slack, but if you could spam them text messages maybe they could still participate, or even participate fully.
Nobody wants to work in IT, especially not for free.
We went thru an internet era, then a social era, then the era of notifications, and I have a gut feeling the next era is going to be something like smooth automatic operations across semi-hostile deeply silo'd platforms, but it'll have a cooler name. FB wants to replace the internet with FB, but literally nobody else wants that, repeat for all platforms, meanwhile you get 5 users together somehow you'll get 6 preferred platforms, the next era will be anti-vendor lockin. People old as me will remember when Ma Bell provided both your phone service and your physical phone and times were better post-divestment and that's probably how we're going to look at the past once we're beyond the era of the social media silo. Rather than "the world is viewed thru my website for my profit" the future will be something like "the world is viewed thru my REST API or maybe many other API providers" And where the profit comes from is mysterious. Likely the gateway tech will be workable microtransactions. Such that every time Sally Softball Mom checks the team schedule she will get billed and you will get a hundredth of a cent, which isn't going to scare away 10M daily users but would be a nice side gig for you personally. Assuming you get 10M DAU of course.
It turns out that complaining about team balance after the match is a feature, not a bug, of the experience for most people and our app was just extra work.