I agree. QBs are a great tool and dare I say it - a necessity. But you HAVE to use them properly. I did all my ATPLs from the QB, Google and YouTube - I didn't open a single book.
QBs are great for rote learning of arbitrary facts: frequency ranges, light signals, how many satellites etc. They aren't so good for questions which require understanding or technique - so of you just learn the answers you'll probably fail.
For example, speed limit below FL100 is 250kts - it's arbitrary and you can't ask that question any other way. In GNav the answer to a question might be 357° true - just learning that is a waste of time. At this point you need to understand WHY it's 357° - so get into Google and YouTube and find out for yourself. (Tell me and I'll forget, show me and I'll remember, let me do it/find it for myself and I'll understand.)
I had trouble with polar stereographic charts. No amount of reading answers or explainations was helping - until i watched a 5 minute clip on YouTube.
The trick with question banks is to recognise what requires knowledge, what requires understanding and what requires technique: Smash the bank, but make sure you do all the working out, even when you know the answer.