Memories can play tricks, it doesnt in this day and age of almost instant research, allow such niave and somewhat negative rosetinted glasses style of posts.
Whilst true the APT-P P for prototype didn't make it into a production train. It allowed a thorough design concept to be trialed over twenty years.
Unions didnt force the build, maybe a reluctance from the outset of the project from the Ministry of transport to provide agreed funds and seemingly constant failure and re-organisation within the management also must have been key. It is hard to make comment on what was clearly a political stance with regard to investment, but my own apolitical thoughts on the matter and based on what information that is public would suggest the project was fixable given the right atmosphere.