Never say never. The most important thing to do is to find the very best school and teachers that you can and then it from there. After you're in reasonable shape, then daily class will be necessary if you want to be professional. It's a huge time and financial investment. There's nothing wrong with dancing for pure enjoyment either. And you can certainly get "good" at ballet even though it's not going to be your job.
Proper ballet training is a slow process. Don't be tempted to take "open" classes at a level which is too high for you. I agree that it helps when there are a few dancers in the class that give you some incentive to work harder. On the other hand, the very fundamentals are extremely important to understand. I've been dancing my whole life and have finally come to understand plie. Tendu is next. Once you have plie and tendu, you understand how to dance.