Learn English – What do you call someone who is banned by law to leave their country? and What is the verb for banning somebody this way

Perhaps self-absorbed

absorbed in one's own thoughts, activities, or interests

or egocentric

regarding everything only in relation to oneself; self-centered; selfish

or self-centered

concerned solely with one's own desires, needs, or interests

SUPPLEMENT

Also consider self-directed

(of persons) free from external control and constraint in e.g. action and judgment

Note that this term is often applied to someone who does attend to the needs of other but exerts a good deal of independence in doing so.

and autonomous

Not controlled by others or by outside forces; independent

Unrealized
As in, unrealized ambitions or aspirations.

It's not a noun but it describes the type of person who has wasted or thrown away an innate skill or talent.

If the OP is determined in wanting a noun to describe a person who squanders his/her talents; I believe many would label that person (perhaps too harshly), as being a loser.

EDIT: In lieu of the OP's comments that the person in question is neither lazy nor immature but on the contrary; a conscientious, devoted parent and son/daughter, the adjective, unrealized, still applies. If the dream was, for example, to be a singer but through circumstances beyond their control that gift failed to blossom. It is common to refer to that person as being an unrealized talent.

Finally, if one wanted to give a more positive and optimistic edge; one could define that same person as being undiscovered.