I don't think we need to look at apprenticeships through a lens that is quite out of date. For example you can look at the apprenticeship schemes in the UK:
This only works with a lot of government support. If you don’t have the government’s ok to take more of the trainee’s surplus in year three than you could if they could just leave why bother training them in year one or two when they’re bloody useless or of marginal value? Unpaid internships exist for the same economic reason; for a long time in many fields the training being provided is worth more than the labour of the trainee. If you can’t get a return from the training why bother? That’s where the government comes in, either by allowing those kinds of contracts or by mandating apprenticeships or levying industry wide “taxes” so everyone pays for trainees’ development and gets the return from it more or less equally. Otherwise the logical thing to do is let someone else pay for the training and then immediately hire away the trainees without paying the costs of the training.
Do you think that apprenticeships in the UK have been successful in motivating training for shortage jobs with highly technical skills?
I don't think they have. I've seen reports which claim they are mostly used as a subsidy to training which was already taking place, as a workaround to pay workers less, and generally in low-skilled jobs.
Like the grandparent post, the UK model is guilty of assuming that the word "apprenticeship" together with a sort of folksy appeal to a golden era of apprentices will solve the hard problems of training and education.
I brought up the past model to show that apprenticeships in the past worked for a specific reason. Various models of apprenticeship/training/education fail today, because we have rejected what made them work in the past. We don't want / can't have a system where young people are completely under the control of an apprentice master for several years, unable to change jobs or live where they want. This is probably a good thing. But without it, the idea of apprenticeships makes little sense.