This, quoted by anuvver poster sums it up perfectly. Now do you get it or do you still fink somefink different and CC should not be bovvered to speak proper?
I am frequently appalled by the poor diction and presentation of announcements on BA flights, and sometimes simply don't know how anyone whose first language isn't British English can possibly understand them. Even the safety demonstration is often rushed or mumbled.
Cabin crew, and especially the younger ones, need to slow down a little and pronounce the words more carefully (just a few dropped consonants, such as you hear in Estuary English, can make an entire sentence unintelligible to a non-native speaker). And those who produce the scripts need to cut out the flowery and superfluous language and simplify the message.
Well, I don't know if you are a non-native speaker but I am so I feel reasonably qualified to speak on what makes things difficult to understand for a non native speaker, or at the very least what things were particularly difficult for
this non-native speaker to understand. The one thing that I found most difficult to cope with when I first moved to the UK was not so much people not "speaking proper", as you put it.It was strong regional accents. Belfast and Glaswegian accents were particularly challenging but plenty of others took me quite some time to adjust to, from rural West Country ones to urban Scouse or Geordie ones.
Pronouncing 'th's as 'f's, which seems to be the bit that seems to particularly irk you as "unprofessional", has never affected my capacity to understand what was said and I suspect that this is true for most, if not all, non-native speakers. It just does not make announcements less intelligible to non-native speakers.
So let us not confuse genuine issues of communication, which most certainly do exist with some speakers (whether they speak "proper" or not), with common garden variety social prejudice.