The eJ safety demo takes around three minutes. If you want to do it one language at a time there's 9 minutes.
Give or take a few seconds for the demo to start in the language.
Do you propose that the demo be shortened to fit it into the three languages in a shorter time? And skip detail?
And your comment about the noise of the PTU is an utter nonsense! Always sit in or near the over wing exits and I've never had a problem hearing BAs safety demo.
Making a comparison to a Scandinavian airline is a little unfair. Being bi or trilingual there is very common. With your modern European large airline you have less chance of crews speaking the languages of the city being served. This would not work with crew who don't speak the languages of the demo.
Sunwing have a safety video in English and French lasting over 8 minutes long. If it were in a third language it would be even longer.