Only you can answer that question. You've gotten good answers.
What is your motivation to paint?
Progression in the craft is ever ongoing-unless one gets to a point and stops.
It is said; proficiency comes as a result of the length of the painting surfaces trailing behind you.
Michaelangelo on his deathbed was reported at protesting; "because he had just begun to see."
I consider 'seeing' to be the most important, and quite difficult, aspect of painting. If you can't see it you can't paint it!
I paint what interests me-for the challenge. I haven't tried to sell any of my works, but I can see the learning progression.
Paint what you're emotional about. The subject can be positive or negative. The 'death knell' generally tolls on subjects you're neutral to. It all comes out via the brushwork. In writing, it comes out via the word choices and sentence construction.
Rhetorical question alert; are the painting slapped together or is each the best you can do at that point of time, or on that day?
Doing your best based on learning and/or that particular day may not be a indication of quality to a particular buyer or buyers. It could also be the right buyer hasn't come across your work yet, or the economics of the person doesn't allow the purchase or many other factors may be involved.
Consider a play written by a sixth grader. Compare that play with one by a playwright. What's the difference between them? Time and learning.