Which metric do we use to define success here? Can shitty software be considered successful just because everyone uses it?
People don't buy the best most perfect fancy publishing platform, they buy something that lets them publish their content and move on with their lives.
I think the success is pretty self-evident?
Sorry for pedantry, but think it helps with the metaphor.
This description != a worthless piece of art.
E.L. James is probably the most obvious recent example of someone who is almost universally decried by the above professions, but still writes something that at the very least is enjoyed by a lot of people. However, there are dozens of - often very successful and much-beloved - writers who fit the same description.
Defining quality in art is a very, very difficult proposition.
On a side note, there are plenty of dreadfully-written, insecure, $register_globals - dependent PHP apps out there solving real problems for real people.
Or, conversely, you're a perfectionist and kicking yourself over the single calculation mistake in an otherwise field-defining paper, masterful performance, etc.
When you participate in a craft, there are measures and standards of quality orthogonal to your emotions, and they matter a great deal in determining whether a work is successful.