As best that I can recall, the Achille Lauro was quite a small ship. Taking over a vessel with thousands of passengers is a whole other ball game.
More importantly, security back then was a relative joke. Security for boarding (likewise, of course, for air travel) is another world today.
Can you imagine "passengers" sneaking assault rifles onboard with their luggage today?
A full on assault at a pier would be possible. For that matter, so could the takeover of a hotel be of concern - there is no security check there at all and an armed band could simply walk right in.
Not something I will be thinking about.