There are both extremes, and best not to be at either one of them.
Example: I forget the name of the principle, but in mathematics the statement "P implies Q" is considered true if P can never be true. As an example, let P be "George Washington was a woman" and Q be "Queen Elizabeth is a man". Then the statement "If GW was a woman, then QE is a man" is considered to be a true statement.
I have a friend who refuses to accept that such a statement should be considered "true". And he has put off studying real analysis until he can learn enough logic theory to convince himself on the validity of accepting such statements as true. I do not think he'll ever get to study real analysis, because he is full of "No! I need to understand this really really well before proceeding!" statements.
It's a fine approach if you have an infinite amount of time.
The other issue, as another commenter pointed out: It's very difficult to measure progress in thought. The mind is great at fooling itself, and not until you try to solve real problems (or discuss them with others) will you expose most of the gaps in your mind. The same person in the above anecdote does suffer from this. He definitely puts in effort to learn a lot (and has succeeded), but there are always more things to learn, and he moves on to the next topic before really applying what he has learned. As someone who talks to him often, it's really hard to tell if he understands. He is the classic case of "I'm sure I can solve problems when I need to, with a bit of review".
At the other extreme, of course, are people who are not really that motivated to understand. They are satisfied if they get the answer at the back of the book. You won't get far with just that.
> If you don't resist them you'll end up moving forward despite feeling confused, sometimes completely. You'll then end up pissing people off when you execute too slowly or fail (in their eyes, intentionally).
This sounds more like an issue at work, and your experience is fairly universal - most jobs I've worked at have it. In my experience, understanding things well is sadly not valued on the job. They want you to "execute", and want you to minimize the time you spend learning. And of course, they would rather hire someone else instead of ensuring your proper learning/training.