In other words, are we confident why Cicero was wrong to insist that most people are experiencing neither pleasure nor pain?
I hypothesize that when Epicurus stated "the feelings are two: pleasure and pain" that it was a "remedy" not a "truth" -- and it is similar in nature to the "remedy" of contemplating that "death is nothing to us". Contemplation of there being only two feelings is a kind of "reframing" of how we think of the nature of pleasure.
And so Cicero had not understood this remedy.
A "neutral" feeling would not tell you if something is desirable or not.