- Reason for the ambiguity between vowel sounds: the organic nature of the mouth.
- Reason why the dictionary’s pronunciation is never going to be like yours: it describes someone else’s accent.
- Reason why the owner of that voice probably doesn’t like that description of their pronunciation: it has been unsuccessfully “dumbed-down” so that we- non-experts- can appreciate it.
- Reason why it is so complex: it was intended to describe every sound possibly made by the human mouth and can clearly show how accents physically come about
- Reason why RP -received pronunciation- was chosen as the international model accent: it wasn't.
RP is a "makey-uppey" accent and it IS dying out. It doesn’t threaten you. It doesn’t threaten me. It is DYING OUT. The accent is described (here in this school) in loads of dictionaries, but it needn't be prescribed to your students any more than my accent should. Yours and mine are not international standard accents. I don't think there will be an actual European/international standard in the future, but I don’t believe there is one right now.
There are clear accents and difficult ones. There are ones where most all English speakers can understand you without asking for repetition and one which require lots of tolerance and smiling and nodding.
Your average native English speaker can make themselves understood to other English speakers if they want to wherever they are from. RP is an accent which is fairly understandable, let's not quibble.
The sounds needed to make a good approximation of RP, an understandable English accent, have been passed down, adjusted and come described most learners’ dictionaries. I want us to enable the learner to approach the dictionary confidently for meaning and use of a word but for its pronunciation as well. This creates more competent learners and gives them the full value for the price of that fun colourful little book.