'not quite good' is a correct and usable phrase in written English. You can use it when you want to describe something as subpar or mediocre. For example, "The food was not quite good; definitely not what I was expecting.".
That's not quite good enough.
"Not quite good enough," I replied.
Instead, it's not quite good enough.
That's not quite good enough, is it?
This is not quite good enough.
Good, but not quite good enough.
"We are not quite good enough yet," another said.
I love the desktop app, it’s always running on my Mac. Ludwig is the best English buddy, it answers my 100 queries per day and stays cool.
Cristina Valenza
Retail Lead Linguist @ Apple Inc.