Whether to quit PhD in psychology: overbearing post-doc, lack of passion for topic, not wanting to enter academia, lack of statistical support
I agree with you that, regarding 1) - difficult co-workers - you very well might quit and have just as overbearing a boss outside academia.  Although it is difficult, that shouldn't be a key driver in your decision. 
(Note that pride is strongest within academia, so working with people who always think they're right is pretty normal!)

However, reasons #2) &amp; 3) - having no passion because you don't think your work is useful to anyone, and being embarrassed about what you do - are very good reasons to seriously consider changing jobs.  This would probably be true in or out of the academic world.

Reason 4) - the fact that you have to learn something difficult all by yourself - may be pretty normal for many different research fields.  However, the thing that often propels people through these difficulties is a passion for what they're doing, either because it's enjoyable or because it feels like it'll be really useful later (to yourself or others).  If you don't feel either of those, then learning the new topics might be quite painful.

Depending on your situation, another option may exist - assuming you, at some point, were really excited about starting research in this field, perhaps  changing projects (or changing the particular aspect of your project that you pursue) could reinvigorate you?

It should be noted that just about every PhD goes through a time similar to what you're experiencing - the end not in sight, too many hurdles, just want it over, along with the constant fear that you're underperforming.  For me, I realized that at least I could say I loved my daily work, and thought it was really cool.  If I hadn't had that passion for what I was doing I wouldn't have been able to make it through the slump(s).