I sometimes get feedback saying 'overall it's good', and I always feel that's saying there's still something lacking and it isn't really that great. Am I reading too much into it?
It's good, overall.
suggests that at least one part of it is not good, without stating this explicitly. If all parts were good, there'd be no need to say "overall".
This is an example of implicature:
From the article: "John ate some of the cookies" does not explicitly say, but still suggests, that not all of the cookies were eaten.
Overall means when all things are considered. Say I go to see a film and the next day my friend asks me how it was. I might start by saying that overall it was a good (or bad) film. This is my assessment of the film as a whole, on balance, taking everything into account.
If I started this way I would almost always then go into finer detail about the good and bad parts of the film, eg
overall I enjoyed the film, although the ending was a bit disappointing
there were some funny moments but overall I wouldn't bother seeing it
If I gave or received feedback on a piece of work this way I would definitely expect the reviewer to expand on what was good and what could be improved, and I think you would be well within your rights to ask for clarification if none is immediately offered.
majority. most. etc etc. its used in english often to give plausible dignity or excusing from 'situational' relevance. O, the sun was shining, food was lovely (BUT, i didnt want to be there), so yes, OVERALL, it was a lovely day. Its actual use in the example i show, is the original ideology of democracy. LOL. You may not agree, but can have input and opinion, wihtout offence and any rudeness, but OVERALL, be agreed, yet obviously, diplomatically opposed.