"Answers per question" is a bad metric.
In a comment to my answer to that post, Jeff Atwood says:
a very high answers per question would be bad. Really bad. 2-3 is
fine; 1 or lower is troubling.
We are at 2.3 right now. That's right smack in the ideal range. I think this shows that we don't need to change anything.
Just because there's an accepted answer doesn't mean that you shouldn't add another if you feel that you can add something significant (if you can add something insignificant, then just edit it unless you desperately want rep). There are even badges to get if your answer is better than the accepted one.
If there is only one answer, and it appeared quickly, and it comprehensively and clearly answers the question about as well as possible, then I think our job is done, and we don't need to be sad that there aren't more answers, or try to add lesser-quality ones somehow.