In theory, you could make it.
In practice, there is a possibility that something could delay you.
For comparison, here is how it's gone for us in 42 cruises: severe delays two or three times out of 42. One was because someone accidentally took our luggage, and we had to wait until literally everyone else claimed theirs before we could make a report.
One was because the ship was delayed returning to the port.
One was because the terrorism alert level had just changed (not long after 9/11), resulting in an insanely long disembarkation line.
We normally use a towncar, so that helps.
Barb