I want to add another angle to this discussion. As a pitching instructor my worst nightmare is a new student who is not an athlete and will not be able to make it as a pitcher. I have had several students like this, they come for lessons, I take their money and feel guilty. Would I ever tell them that they're wasting their time? No, but in at least one case I wondered if I was doing them a disservice.
I spoke with the owner who said it’s too late for her to seriously jump into pitching as other girls at her level are already pitching FAST and developing/perfecting their 3rd pitch. It was also stated that her birthday puts her at a disadvantage coupled with being a grade lower (currently 7th grade) than 14u competitors. She said she’ll never pitch in travel so what’s the point of doing lessons for 1 season of rec?
It is difficult for me to understand the mindset of some coaches/instructors. In my opinion, it is not their job to help the player become the best in the world. After all, there is only one best in the world, right? It is their job to help the athlete become the best they can be. Whatever level that may be. Maybe it's pitching in a rec league. Maybe it's pitching in high school. Maybe it's a D1 scholarship. Whatever the end goal is doesn't matter, as long as the athlete enjoys what they are doing.
That said, I have no issue with a coach sharing some perspective. For example, stating that she will be at a disadvantage against athletes with more experience is justifiable, but probably already known.
I tend to compare coaches/instructors to teachers. Imagine if a child is struggling with math or some other subject and goes to their teacher for help. The teacher says, sorry, you just don't have what it takes. You may as well just give up. A reply like that is simply unacceptable. I feel the same way about the instructors reply to the OP. Unacceptable.