Desert witch
I do not have the numbers about demotions and/or failures. There is just a few things, I would like to shed another light on. Trainer don't fail anyone. It's examiners that fail. Trainers conduct a training session and if unable to train to a minimum required standard they have to give a developing grade in order to allow training management to assign additional training. If too many additional trainings are required, fleet gets involved to decide if training should be continued or not. It's not even Training Management to do this.
If a developing grade is awarded it could be the trainers inability to train properly or, from what I have experienced more likely, the "material" to work with is not trainable in the time available.
Certainly some of the newer joiners are not of the same average standard as about 10+ years ago. We still get excellent pilots which never have a problem. But we get more than before of the other type as well. Career prospects, roster issues, leave issues... you name it, makes it more difficult to attract the required quality. Don't blame the trainers, nor the examiners if they don't lower the bar.
Unfortunately not all pilots are quite as good as they think they are.
Should the company provide more time to train? Yes absolutely (and thinking back to my upgrade preparation, or lack of, they do). But this is not the trainer's nor Training Management's decision. That goes to OPS Management and is all about money. How much can safety cost....
Not trying to defend anyone's position, just a few thoughts from the inside.