Should we slip a release to get a bug in? I have an opinion. Is that really a bug? I have an opinion.
How expensive is this feature? I probably have an opinion. Of course, my opinion isn't always the way we wind up going, but that rarely stops me from having one!
Sometimes, though, I really don't have an opinion. Sometimes there isn't one option better than another. Sometimes I'm simply not informed enough to have an opinion. Sometimes I don't even know there's a choice to have an opinion about. In all of those situations, I could form an opinion, but it would just be more likely to be wrong. Better to not have an opinion than to jump to a conclusion.
It's okay to not have an opinion, as long as you know why you don't have an opinion. It lets you know what pieces you're missing.
Of course, having no opinion only works for so long. At some point a decision has to be made and that's probably based, at least in part, on your opinion. The trick, then, is to figure out why you don't have an opinion, get the data you're lacking, and arrive at a well-formed opinion.
Therein lies a the root of a good decision.