I've learned from personal experience that there are two types of not good enough when people tell you that what you've produced and shared isn't good enough.

The first kind

The first kind of not good enough is an accurate designation. The person who is saying this to you is telling you from a place of genuine observation or concern that what you've produced isn't good enough to cut it.

The second kind

The second kind of not good enough is an inaccurate designation. The person who is saying this to you is either too biased, self-interested, insecure, or limited in their thinking to see that what you've produced is good enough to cut it.

So what?

It's up to you to decide which not good enough you are encountering, and then react accordingly.

And if it's the second one, don't listen to whoever is saying that what you've produced isn't good enough.