As a college coach...
I get a ton of unsolicited emails from "prospects." Probably two or three a day during the fall. The vast majority of which I am not interested in. I use to send a form email thanking the athletes for their interest, that also indicated minimum performances needed for consideration. I found though that any email back to prospects led them to keep emailing, which is tedious.
I think most coaches ignore emails from athletes they are not interested in; and it is all right for you to do the same.
If you get to the point of phone calls and visits with a coach that is when it is no longer OK to ignore an email or call. If you or the coach want to terminate the recruitment process the other person is owed a response; it can be as simple as I am no longer interested.
You do need to figure out what you want in a school. Respond to any programs you are interested in.