I doubt carriers would ever agree to a single, unified, understanding of 'departure' and 'arrival' because, some of them would have their timings get worse and some would have them get better.
For myself, I think that, for all the shouting about good time keeping by the kids in
PR and consumer groups - the public will generally go for the lower price and accept the delays!
For all that, delays are endemic to the business and are not going to improve - particularly in the UK and Europe.