The term "armchair" is used a lot. An armchair critic gives opinions on subjects they haven't directly experienced. An armchair mechanic might say something won't work from a mathematical standpoint despite people doing it in their garages all the time. An armchair activist yells at the TV about how we all need to get up and do something about whatever political situation they don't like, but who never gets up to do anything themselves (this case also qualifies as hypocritical).
This isn't quite the same as your example though. In your example, you're talking about a purely subjective thing, while the use of "armchair" tends to be more objective. I'm not sure that "armchair pie-taster" works as well.
Of note, just because someone hasn't tried something doesn't mean they can't objectively determine that they would subjectively hate it. As an extreme example, I can be pretty confident that I would dislike getting shot with a gun without getting shot first. Similarly, I can use my experience in other fields of study to make a pretty good argument for a field of study I don't have experience with.