I can think of one open source project where the developers tend to work on things they’re interested in, not on things that might make life easier for users of that product. Use-case is always a matter of perspective, users of products have a different view of use-case than developers do. Developers tend to think of things users do as ‘just more data’, and often don’t see how a small change might make a HUGE difference in usability. (I’ve done my share of system development, and I’m sure I’ve had that attitude at times.)
So far I can’t say I’ve seen that kind of attitude with Discourse development, but I’ve only been here a month.
As to being too close to the product, I’m currently going through the exercises in a book on Ruby development, A simple ‘hello world’ app took me 3 hours to get working yesterday, mostly because the book assumed familiarity with an AWS IDE (cloud9) environment that I didn’t have yet, so I’d click on something and it’d undo the changes I just spent 10 minutes typing.
And then there was an issue with getting a preview of the working app to display on my browser, which appears to be due to security limitations that both Firefox and Chrome have put in their browsers since the book was last updated. After an hour or so of web-searching for solutions, whitelisting the IP address of my laptop and desktop worked, though I still have to go through an extra step to get the preview to display.