All aircraft have to have any number of "holes" in them just to exist. (From a geometric aspect, there's no "inside" to a solid plane.)
Jet engine is a giant hole through and through, if with some intervening "bits" to make it work.
An aircraft with no holes in it would mean you'd need to bring your own tank of breathing air.
If we are putting a fine point on it, most aircraft are only pressurized to around 8-9psi, any more creates even more discomfort for passengers (only takes about 1/2" of water column to cause discomfort at the 75th percentile).
Also, as any aircraft maintainer--there's no such thing as a "perfectly good aircraft"
Shoot, far too many seem to have stopped dressing at "underwear" and barely that, as is. The number of open-toed shoes is directly proportional to how awful the exposed toes look, too.