Smart people spend lots of time learning, thinking about things, and relying on their (often overactive) imaginations. It's not surprising that spending so much time in your own head can sometimes lead you astray.
A helpful response would be to reassure and encourage your peers. Point out when there's objective evidence that they are doing a good job, because they may not be able to see it on their own.
In this light, the attitude displayed by the current top level commenters is extremely disappointing [0,1]. Insinuating that your coworkers are slow or out of their depth in circumstances like these is counterproductive. IMHO, this "maybe you're just not good enough" attitude is one of the most toxic aspects of living in silicon valley and the bay area.
I am a perfectionist, and I know that I waste gobs of time over-analyzing absolutely everything [2]. I also know that my best work only happens when I force myself to set aside that perfectionism and just start. It doesn't matter if it's terrible, it doesn't matter if I picked the wrong library -- wasting more time over-analyzing everything never gets me anywhere, and leaves me feeling miserable at the end of the day.
I know, objectively, that this is the case, and yet I still hesitate to start big projects, and still attempt to use spreadsheets to plan the most trivial of things. It's not an easy habit to break, but it's absolutely worthwhile to keep trying. I owe a lot to the peers and managers who have helped me stay on track.
[0] https://news.ycombinator.com/item?id=16335156