I don't have time,'' it's ''I couldn't do it justice,'' or some other excuse. No excuse is valid. You do not become a writer by wishing, or talking about it, or by pitching ideas to writers. You might possibly become a screenwriter by pitching story ideas to producers, but that's another category entirely. For one thing, writers aren't in the business of helping other people write, and generally have plenty of ideas of their own.
Ideas are cheap.
Either make time, or forget about becoming a writer. Then practice writing until you can. Ray Bradbury burned his first million words because they were unsaleable garbage. Most writers started out writing reams of garbage. I sure did.