It's a craft...
If you think your art isn’t good enough, the question is - why not? The next question is - can you see what you have to do to make it better? After that you have to ask yourself if you are prepared to put in the years of work and commitment in order to become that good?
Be warned - as you improve, and learn, you get better at seeing what makes art great, so you continue to kick your expectations of yourself down the road, meaning you can never really get as good as you’d like. But also know - this is a GOOD thing! You’ll forever keep reaching, and keep getting better.
Stagnation comes from complacency, or believing you are already as good as you'll ever be.