There are three different situations here.

1. Engine failure. Every multi-engine aircraft, not only commercial jets, is designed to fly, maneuver (perhaps in a restricted sense, especially as regards turning toward the side with the most remaining power) and land safely with one engine out. Pilots are trained to handle this situation.

2. Engine removed. In the totally hypothetical situation that an engine were designed like a drop tank, so that it could be physically released with no other damage to the aircraft, most multi-engine aircraft should still be able to fly and land. To my knowledge nobody has ever designed an airplane with quick-release engines (other than a few special-purpose takeoff assist rockets). I'm certain no commercial jet has them.

3. Engine falls off. Here the problem is that, if an engine that wasn't meant to fall off does, it will cause a lot of airframe damage in the process (or there was a lot of airframe damage that made it happen). It's this damage that creates the largest share of problems, not the lack of one engine's power or even the lack of the engine itself.

Unfortunately, the recent event was a #3.