I'm confused. Your title says "adjective" but your question asks for the name of the person, which would be a noun. adjective: unpersevering, unambitious, lazy, shiftless, loafing noun: dabbler, quitter, goof-off, slacker, loafer

A "jack of all trades" has an adequate knowledge of many areas but is not specialist in any. It's maybe more positive than what you had in mind. A "dabbler" tries different things but not seriously. It doesn't imply boredom but more lack of serious intent. You could say: "He/she is like a butterfly" as this metaphor expresses transience e.g. a social butterfly is someone who spends a few minutes talking to someone e.g. at a party, before moving on to the next person.

i think the word that you want it ... is not exist in any dictionary !!