Attention to detail is important in producing a convincing picture - as SamTherapy commented, there are plenty of examples to be found which seem to lack even the most basic self critique. However, I can find many of these faults in my own early works - we're all part of a learning process, or else why are we here?

You do need to know where to stop though, since there's a point of diminishing returns beyond which you'll put in loads of work but won't get any noticeable improvement. This point will vary according to the artist. Reading between the lines of your first post, it seems that you have concerns about your level of involvement, in which case it might be helpful if you learned when to let go of a project. ;)

Postwork was the key for me. Once I have the render as good as I can get it - expressions and body language sorted out, lighting optimised and so on - I take it into PostworkShop and deliberately transform it into someting that is evidently not intended to look realistic. That saves me from agonising over the last 5% of realism that I'm probably never going to achieve.