Anyone can take piano lessons or tennis lessons. Not everyone is going to be a Horowitz or a Venus Williams. Anyone can learn to do a sport or take lessons on an instrument. Not everyone is going to be a professional or even reach professional calibre.
Does it mean then that only the very talented should be given the option of having lessons? Of course not.
Years ago, however, the philosophy was “you either had talent and a voice and could sing” or you were “not talented, had no voice, and should never sing” and there was very little in between. If, in addition, you could not readily match pitch, then you were deemed hopeless.
Thankfully, this idea is mostly gone now. Most people who teach singing know that anyone can be trained if the teacher has the correct skills to do so and that most people, if they practice and are patient, can learn to sound quite good, even in classical repertoire, over a length of time, usually anywhere from two to five years.
I have had several adult beginners go from sounding pretty bad to sounding quite good just because they were diligent and dedicated and did not give up lessons or practice. This is no miracle, it is skill development. Perhaps they are not naturally inclined to be easily expressive and emotionally powerful, but that isn’t always necessary, as there is repertoire that is less intense to perform and less challenging to communicate effectively.
Talent is a combination of many things. In terms of singing it means that the sound of the voice itself is interesting in some distinct way. It means being musically expressive easily and also means being able to hear music easily and accurately, even if the singer does not have literacy in musicianship. It can include other skills as well, but those listed here seem to be typical in evaluating “natural ability” and they are certainly good things to have if one wishes to sing. However, many people who have careers are not given great assets in any of these categories and succeed anyway.
The goal of training in singing is to create a bridge between physical skill and artistic expression. It is very frustrating if you have a deep desire to express yourself through singing and you have limited ability to do so. It is very challenging to bring enough emotional truth to the singing to make it compelling without also knowing how to get your voice to stand up to that level of expression, although some people do manage. It is difficult to have a lovely voice with a nice delivery but have not much to say in terms of communication. I have worked with quite a few people over the years who had absolutely no depth as artists and, in fact, didn’t at all understand what artistic depth was, yet they had financial resources to go out and hire arrangers, publicists, and back-up singers and create decent careers anyway. Amazing to watch that, really.
Creativity is unbounded. Human beings likewise. Training not so much. Training has to have a goal, a purpose, a direction and it has to have some kind of organization or else it is really just experimentation, trial and error and guesses. That could work well enough but it could take decades to get anywhere consistent and no one really has that much time to spend before getting to a place that does the job well.
If you teach, build a bridge, but know what kind of a bridge you are building.