I get what you mean. Gifted children who have expert (usually, but not always expensive) teachers, parents who have the time and/or money to allow their participation in lots of musical activities and a good instrument will usually be more advanced than gifted children who don't have these. However, an unmusical child given the best and most extensive training will never be as good as a musical child who has had the same amount of training. A prodigy is usually someone who is not only super talented, but also has a very high level of concentration, very high level of interest and enjoyment in their area of expertise and at least average levels of energy; these attributes must be present alongside the natural talent for truly exceptional skills to develop.
However, child prodigies don't always go on to be successful in their field. Sometimes they are exceptional for their age, but are overtaken by their peers as they get older.
Why on earth would you want your young child to write and direct an opera? How does that child relate to their peers? You are very wise to not want a career in music for your DC.
I suspect the problem at conservatoire level is that the ones who have the best technique and most musical experience are seen as a safe bet. The fact they enter at such a high standard is just too tempting for the conservatoires and indeed youth music groups with the result that musical potential is not always nurtured.
A regional orchestra regularly has no children from glasgow education authority! I don't believe glaswegian children are less musical than children from anywhere else. The glasgow children who get in are usually privately schooled.
My DS is musically gifted ( perfect pitch, scholarship holder at a london conservatoire) but he wasn't a prodigy. He started playing double bass when he was 12 and succesfully auditioned for a conservatoire aged 17 ( admittedly double bass isn't nearly as competitive as most other instuments, especially when his course is jazz ). It was very obvious that he absolutely loved jazz, once he discovered it at his state school. He spent most of his free time listening, playing, reading about jazz and practising. It very much came from him. But yes, he also got a lot of support from me and his relations.
Some musical genres aren't recognised as much as classical, which also contributes to the rich prodigy phenomenon. Eg jazz, for which you have to be astonishingly musical or hip-hop, or traditional music.