This is very true these major problems couldn't have been foreseen by enthusiasts, but they should have been by the project managers. I study building design/production and project management, I'm not an expert but I can say these are certainly bread and butter for any project. Same for a lot of Merlin projects, these things are known about but corners are cut relentlessly.
Same for Ninjago's lack of air conditioning at Legoland – cut from the budget to save money and now we have staff fainting in summer and cheapo air cons added at the park's expense. But anything to cut MMM's project budget. Or countless other scenarios at Merlin parks, that later cost them more.
But the irony with DBGT is the project budget was so ludicrously high anyway, they could have rebuilt half the park with that! As well as cutting corners and not value-engineering their projects, Merlin are extremely wasteful. "Efficient with capex" they are not, unlike what Nick Varney believes they are.
But probably more important than all of that is the entertainment factor. DBGT is a pretentious, unentertaining load of nonsense, designed by self-congratulatory out of touch hipsters. (haha) Despite all the problems behind the scenes, it had the beginnings of a great theme and should have at least been fun!
I totally agree the core idea and the way the illusion works could have been phenomenal. But it missed every single opportunity to entertain, and squandered that amazing train system.